There are 3 types of Classes for a Weapon: A, B, and C. A weapon can only have one class. The following info reveals a description of each class:
Class A- Your main weapon. A character can only have one main weapon. However, if they are a Dual-Weapon user, they have the exception of using two.
Class B- Your alternate weapon. These weapons are used if you find yourself in a position where the effects of your main weapons are ineffective in a particular situation. A character may only have 5 alternate weapons.
Class C- Your last resort. In this particular area, a character may only have one weapon of this kind. A Class C weapon may only have one effect. This effect adds an additional effect to an already-used weapon, and repairs it to its rightful condition.