There are a total of six modes in Mario Party 4: Party Mode, Story Mode, Mini-Game Mode, Option Room, Present Room, and Extra Room.
Party Mode
In this mode, you can play on any map you want.
Party Mode is pretty much the same as it has been in every other Mario Party game. You can view the rules of the game, select the number of human players, pick characters, and choose a board to play on. The major change to Party Mode is that now, players can be divided into two teams of two, in addition to the normal Battle Royal. The turn amount ranges from 10 turns to 50 turns in increments of 5, and there are star handicaps for less skilled players. There is also the option of only using the "Easy" Mini-Game set.
The goal in Party Mode is to collect coins and use them to obtain the most Stars. Coins can be obtained through the various spaces on the board and by winning the Mini-Game at the end of every turn. If the Bonus Star option is on, players will receive Bonus Stars depending on how they did in Mini-Games, their Coin "Record", and the number of Happening Spaces they landed on. For detailed instructions on how to play, see the Rules section.
Story Mode
Follow the story in this one-player mode.
Story Mode is similar to Party Mode except for the fact that only one human can play. The goal is to win all six boards, receiving a present from each character that hosts a board. Gameplay in the boards is identical to the Party Mode gameplay. After successfully winning a board, you must play a Story Mini-Game against the board's host before receiving a present. There is an extra "present" you will receive after receiving all of the presents from the board hosts. Completing Story Mode on the Hard difficulty setting unlocks the Intense difficulty setting for all other modes. Completing Story mode is also the only way to unlock the final board, Bowser's Gnarly Party.
Mini-Game Mode
Play all the Mini-Games you have unlocked in other modes.
Mini-Game mode is divided into 4 main components, some of which include more modes.
Play
You won 'em! Now you can play 'em!
As the title suggests, this mode allows you to play any Mini-Games that you encountered in Party or Story Mode. There are four modes contained inside of Play mode.
Free Play
This mode allows you to pick and choose any Mini-Game you have unlocked and play it. For games divided into teams, Player One gets to pick which players are on the same team. Free Play mode is the only way to play a Story Mini-Game against a character other than a board host.
Team Play
Battle Mode
Tic-Tac-Toe Mode
This mode consists entirely of 2-vs-2 Mini-Games, and players are divided into two teams. It works just like the game Tic-Tac-Toe except for one catch. Your team only gets a block if they win the 2-vs-2 Mini-Game. The first team to get three-in-a-row wins.
List
This pulls up the same menu as in Free Play mode, but this time, the Mini-Games aren't playable. It's good for quickly checking which modes (e.g. 1-vs-3) are complete and which ones still have Mini-Games missing.
Custom
This pulls up the same menu as in List and Free Play mode. However, you can add Mini-Games to a Custom list. You can have up to four 4-Player Mini-Games, three 1-vs-3 Mini-Games, three 2-vs-2 Mini-Games, and two Battle Mini-Games in your custom list.
Records
It pulls up a list of records for Mario Medley, Domination, Right Oar Left, Dungeon Duos, Mario Speedwagons, and Take a Breather. This is very helpful for seeing which Mini-Games haven't yet unlocked a present yet because the record is too slow.
Option Room
Change sound settings and view game statistics.
Present Room
Check out all the presents you have received.
Extra Room
Play some extra Mini-Games.