A class is the primary adventuring style of player characters which determines the type of weapons and armor they can use, as well as what abilities, skills, and spells they will gain throughout their adventures. Be aware, choosing a class is constrained by the choice of race.
As characters progresses they can specialize their skills by assigning class talent points in one of three trees available for each class. Collecting class sets is also a major way of progressing a character when they have reached the level cap. Most dungeon and raid sets are made up of armor items designed specifically for the class, however faction rewards sets also include trinkets and neck pieces.