Mount&Blade: With Fire & Sword/Proficiencies

The proficiency rating of weapons will determine how good you can hit with a weapon (dealing more damage) as well helping you to aim with ranged weapons.

You can add points by training, fighting or at the end of each level.

If you add a point to agility you will get +5 extra points to add to you proficiency.

Note that you will have to keep your weaponmaster attribute high enough to train faster. The higher this attribute is the less points you need to spend for each level. sometimes you even raise 2 levels with one add of a point.