Believe it or not, all of the above information I would consider "Basic Knowledge" to Pokémon. Now, we're in the land of "how to use it", not "what is it". Pokémon has a "Job System"; the moveset of each Pokémon determines its job. If you're with me so far, then you should know that "The Job System" is not an official system, but it is there for competitive battlers to reference and put their Pokémon into categories. Most of the terminology mentioned before is official. From now on, most of the terminology will be player-created, since the players will take the information that is given and analyze every inch of it.
As I described above, Pokémon's moveset determines its place in the "Job System". Some Pokémon can only do (or be proficient at) certain jobs, depending on its type and stats. Also, I will start referencing "Base Stats" of Pokémon. If you remember, "Base Stats" are not the stats of a Pokémon at a level, but it is rather an average ratio used for comparison purposes. I will try to define all of the terminology as well.
Physical Sweeper
Physical Sweepers are called so because these Pokémon figuratively "sweep," or take down many Pokémon. As you can guess, Physical Sweepers use Physical Attacks efficiently. A good Sweeper would be able to take down at least two Pokémon before fainting. Here is an example of a Physical Sweeper. This is also a good chance to get used to the format for describing a Pokémon:
Heracross (F) @ Leftovers <-- Species, Gender, and Attached Item
Trait: Guts <-- Trait
EVs: 58 HP / 252 Attack / 200 Speed <-- Effort Values Distribution
Adamant Nature (+Atk, -SAtk) <-- Nature
-Swords Dance <-- First move
-Focus Punch <-- Second move
-Megahorn <-- Third move
-Rock Slide <-- Fourth move
This is the proper way to present a moveset. Although all of the information above is not necessary, it is good to have the Pokémon's moves and Nature. Regarding the moveset above, Heracross will Swords Dance to double its Attack, then Focus Punch, Megahorn, and Rock Slide will totally devastate your opponent if your opponent does not have a Pokémon that resists these moves. Note that just having four attacks on Heracross is not as effective as having Swords Dance and three attacks. This is an example of how Stat Changing moves and Damaging moves can work together to create a good moveset.
Special Sweeper
Special Sweepers are other Sweepers that use Special Attacks. Here is an example of a Special Sweeper:
Starmie @ Leftovers <-- Some do not have a Gender
Trait: Natural Cure <-- Its other Trait has no effect
EVs: 42 HP / 216 Speed / 252 Special Attack
Timid Nature (+Spd, -Atk)
-Surf
-Ice Beam
-Rapid Spin/Thunderbolt <-- "/" indicates own preference
-Recover
Notice now this Sweeper does not boosts up its attack power, but instead boosts up its staying power with the move Recover, so it could faint less quickly and deal more damage. Also notice something about the Effort Values of both Sweepers. Usually, maximum (252) EVs go into Attack or Special attack, depending on the type of Sweeper. There are also many EVs on Speed, since a Sweeper that attacks first takes less damage. The Nature of Sweepers often increases Attack, Special Attack, or Speed also.
Mixed Sweeper
Mixed Sweeper is merely a Sweeper that uses both Physical and Special Attacks. There aren't many of these, since it is better to specialize in either Physical or Special. However, there are a few Pokémon that make good Mixed Sweepers, and here is an example:
Swampert (F) @ Leftovers
Trait: Torrent
EVs: 38 HP / 128 Attack / 220 Special Attack / 124 Special Defense
Brave Nature (+Atk, -Spd)
-Curse
-Earthquake
-Ice Beam/Surf
-Rest
Once again, Rest is for staying power so Swampert can come back and sweep some more. EVs are a problem for Mixed Sweepers because it is hard to know how many to put in Attack and how many to put in Special Attack. Curse takes care of that problem, since using Curse lets you concentrate more on Special Attack and other stats while giving reduced contribution to Attack. If you don't know, Curse increases Attack and Defense one stage while lowering Speed one stage. The reason this sweeper doesn't need Speed is because Curse makes it powerful defensively also, not just offensively. Since it's also defensive, it doesn't need to go first. Note that Physical and Special Sweepers usually have high offensive stats but low defensive stats.
Hazer
A Hazer is a Pokémon that uses Haze. Since Haze is such an important move, there are Pokémon that are designated to do this job. Here is an example of a Hazer:
Weezing (F) @ Leftovers
Trait: Levitate <-- Weezing is now immune to Earthquake!
EVs: 196 HP / 156 Attack / 158 Defense
Relaxed Nature (+Def, -Spd)
-Sludge Bomb
-Haze
-Will-O-Wisp
-Pain Split/Rest
In case you are wondering, yes, there is a reason for choosing only female Pokémon. Male is the default Gender online, so many Pokémon using Attract are Female. For this reason, I use Female Pokémon so they can't be attracted.
Of course, a Hazer can't just Haze; it needs to have other jobs as well. Hazers are usually Tankers or Walls (more about this later), or Pokémon that can stall for a long time. This is because it needs to Haze many times if your opponent keeps Swords Dancing.
Pseudo-Hazer (PHazer)
A PHazer is a Pokémon that usually uses Roar or Whirlwind to force switching. There are other exceptions, but that will be explained later. PHazers are very similar to Hazers, but they are more popular because many Pokémon learn Roar. Here is an example of a PHazer:
Suicune @ Leftovers <-- More Leftovers? Yup, good item.
Trait: Pressure
EVs: 252 HP / 128 Defense / 64 Speed / 64 Special Attack
Bold Nature (+Def, -Atk)
-Calm Mind
-Surf
-Rest
-Roar
Like Hazers, PHazers need to last, so Rest is included in the moveset.
Physical Tanks
If you guessed it, Physical Tanks are intended to take damage. These can also deal damage, but usually through indirect moves, with a possible addition of one damaging move that does not have to deal a lot of damage. Usually, it's Toxic or Will-O-Wisp plus Rest or Recover on a Pokémon with a very high Defense. Here is an example of a Physical Tank:
Steelix (F) @ Leftovers <-- Notice how it's immune to Sandstorm
Trait: Sturdy
EVs: 252 HP / 80 Attack / 42 Speed / 136 Special Defense
Impish Nature (+Def, -SAtk)
-Earthquake
-Rock Slide
-Explosion
-Toxic
Steelix resists many Physical Attacks but can still dish out some damage. Steelix can never be a sweeper, but it serves its purpose as a Physical Tank well. In fact, Steelix doesn't even need Rest because it takes so little damage from Physical Attacks.
Special Tanks
Of course, Special Tanks are the Special version of Physical Tanks. Here is an example of a Special Tank:
Regice @ Leftovers
Trait: Clear Body <-- Opponent cannot lower stats
EVs: 200 HP / 200 Defense / 56 Special Attack / 54 Special Defense
Bold Nature (+Def, -Atk)
-Ice Beam
-Thunderbolt
-Thunder Wave/Counter
-Rest
As you have guessed, neither Ice Beam or Thunderbolt will do much damage, but Regice is extremely tough to take down.
Walls
Of course there aren't many Mixed Tanks. Why? Their Defense and Special Defense stat is so high that they have no Attack or Special Attack at all! Of course, I'm talking about Shuckle, and for the sake of simplicity, let's just focus on Walls. Walls are like Tanks, but they are not expected to damage their opponents in any way. However, they are expected to take more hits than Tanks, so this job is for people who like to take their battles slow and steady. Here are two good types of Physical and Special Walls. There aren't many, so that's why they're in the same category:
Skarmory @ Leftovers
Trait: Sturdy
EVs: 196 HP / 30 Attack / 252 Defense / 32 Speed
Impish Nature (+Def, -SAtk)
-Spikes
-Drill Peck
-Rest
-Roar
Blissey @ Leftovers
Trait: Natural Cure
EVs: 240 HP / 252 Defense / 14 Speed / 4 Special Attack
Bold Nature (+Def, -Atk)
-Aromatherapy/Heal Bell
-Softboiled
-Seismic Toss
-Ice Beam
These two Pokémon often work together as a team and they make great Walls. Of course, they will probably not defeat any Pokémon alone, but they will resist most attacks thrown at them.
Cleric (Healer)
Clerics use Heal Bell or Aromatherapy to rid their team of Status Effects. These are very helpful if you encounter an opponent that tries to Paralyze your team to death, or if you have a Sleeping Pokémon on your team because it used Rest. Clerics are, as predicted, good tankers, so they can keep healing the party. Of course, one great Cleric is Blissey. Here is an example of another Cleric:
Miltank (F) @ Leftovers
Trait: Thick Fat <-- Trait makes it a good Tanker.
EVs: 168 HP / 172 Attack / 168 Defense
Adamant Nature (+Atk, -SAtk)
-Curse
-Body Slam
-Milk Drink
-Heal Bell
Annoyer/Staller/Drainer
Annoyers annoy the daylights out of most people, using Double Team, Confuse Ray, Thunder Wave, Attract, and Rest as some popular annoying moves. Unlike Tanks and Walls, Annoyers don't absorb hits--they evade or try to make their opponents unable to attack. Sometimes, Heal Bell and Roar can send Annoyers packing. Sometimes, Annoyers are unstoppable after many Stat Changes. I put Annoyers and Drainers together because most Annoyers find a way to replenish their HP, and it's usually from Leech Seed, Mega Drain, or Giga Drain. Here is an example of a Drainer:
Ludicolo (F) @ Leftovers
Trait: Swift Swim
EVs: 252 HP / 130 Defense / 128 Special Defense
Calm Nature (+SDef, -Atk)
-Leech Seed
-Toxic
-Protect
-Seismic Toss
I know Ludicolo can regenerate HP with the Rain Dish Ability, but this is a great Rain Dance counter since an Annoyer that goes first is very powerful, and Ludicolo can restore HP with Leech Seed instead.
Spiker
A Spiker uses Spikes. You've already seen a good Spiker, and that is Skarmory. However, Skarmory is not the only option, because if you want a Spiker as a starter (your leading Pokémon), then other Spikers are better. If you use Skarmory first, there is a chance that you will get eradicated by a Magneton with the Magnet Pull Ability. No example for now, because I'm going to introduce to you another job first.
Spinner
A Spinner uses Rapid Spin to get rid of those evil Spikes. You've already seen a good Spinner, and that is Starmie. But hey, a Pokémon can have two jobs, and a Spiker/Spinner combination is actually very good. Here is an example of a Spinner that is a Spiker as well:
Forretress (F) @ Leftovers
Trait: Sturdy
EVs: 252 HP / 70 Attack / 188 Defense
Impish Nature (+Def, -SAtk)
-Spikes
-Rapid Spin
-Earthquake
-Explosion
If Forretress encounters another Spiker, then it will Rapid Spin after a few Spikes. Note that Rapid Spin only rids you of your opponent's Spikes, and the Spikes you have set will remain in play. After three Spikes, or when it thinks that it will faint, then it uses Explosion, getting rid of a Pokémon. Of course Earthquake is there for a damaging move, although it is rarely used.
Baton Passer
A Baton Passer uses Baton Pass. Usually BP stands for Baton Pass and BP'er stands for Baton Passer. A BP chain includes two or more Pokémon Baton Passing different Stat Changes and finally Baton Passing to a nearly indestructible Pokémon. However, a BP chain should be aware of Hazing and Pseudo-Hazing. Since I can't decide on which example to show you, here are examples of two Baton Passers:
Scizor (F) @ Leftovers/Leichi Berry <-- Increases Attack at 25% Health
Trait: Swarm
EVs: 110 HP / 108 Defense / 128 Speed / 164 Special Defense
Careful Nature (+SDef, -SAtk)
-Swords Dance
-Agility
-Hidden Power
-Baton Pass
Ninjask (F) @ Leftovers
Trait: Speed Boost
EVs: 6 HP / 252 Attack / 252 Speed
Adamant Nature (+Atk, -SAtk)
-Swords Dance
-Substitute
-Silver Wind
-Baton Pass
Ledian (F) @ Leftovers]
Trait: Early Bird
EVs: 110 HP / 164 Defense / 128 Speed / 108 Defense
Impish Nature (+Def, -SAtk)
-Swords Dance
-Agility
-Baton Pass
-Aerial Ace
Plusle (F) @ Leftovers]
Trait: Plus
EVs: 6 HP, 252 SAtk, 252 Spd
Timid (+Spd, -Atk)
-Nasty Plot
-Grass Knot
-Baton Pass
-Thunderbolt
Scizor is not a Sweeper, but if its current opponent poses no threat to Scizor after at least one Swords Dance and one Agility, then use Hidden Power (Bug-type) to get rid of that Pokémon, then Baton Pass. It is the same for Ninjask. If Ninjask's Substitute is not broken, then Silver Wind after Swords Dance could do wonders. Ledian can also be effecive, so long as the foe does not have a Rock-type move, and Aerial Ace can hit everything (including the infamous Shedinja). Plusle's Nasty Plot can prove effective if the Plusle is with Minun and against a Pokémon weak to Electric or Grass, and if it's something like Shedinja or Wormadam, Plusle can Baton Pass, although you may want to sub Thunderbolt for Thunder and give Minun Rain Dance. But getting back on topic, just think how good Heracross, Flygon, or Machamp is with Swords Dance and Agility Baton Passed. Their Attack and Speed would have been doubled!
<Insert Move Here>'er
Okay, so that's not really the name of the job. Basically, adding the suffix -er to any move can make it a job. You will commonly hear Tyranitar makes a good Dragon Dancer or Suicine makes a good Calm Minder. There are very few moves that have -er added after it though, because only moves that could significantly benefit a Pokémon would be a candidate. I assume that you don't need an example, because it's pretty self-evident what I will put. If you really want an example, then scroll up and look at Suicune's moveset (Calm Minder) or Heracross' moveset (Swords Dancer).
However, there is a point that I should make. Sometimes, we competitive battlers get lazy, and certain abbreviates starts to pop up. For example, CM stands for Calm Mind and CM'er is a Calm Minder. DD, SD, and ST stands for Dragon Dance, Swords Dance, and Sleep Talk, respectively.
Other Jobs
There are many other jobs, but they have become forgotten or unused when the Third Generation comes out. Generally, we consider the Third and Fourth Generations' battles to be of a faster pace, so many stallers or indirectly damaging Pokémon are out. Some examples are Toxi-Shufflers, Para-Shufflers, and Perish Trapper. I will only briefly describe them as most attention have now focused on the Third Generation and many battlers do not battle GSC much anymore.
Toxi-Shufflers
These Pokémon use Toxic then Roar or Whirlwind so all of their opponent's team's Pokémon are Poisoned.
Para-Shufflers
These Pokémon use Thunder Wave then Roar or Whirlwind so all of their opponent's team's Pokémon are Paralyzed.
Perish Trapper
Perish Trapping is not really gone, but it's not really for one Pokémon anymore. In GSC, one Pokémon uses Mean Look and Perish Song to prevent the opponent from switching out of the inevitable fate. However, in RSE/FRLG, there are much more opportunities to faint that Pokémon before it uses this combination, so two Pokémon must Perish Trap. I will give examples as the guide progresses.