The third edition of Dungeons & Dragons (3E) resolves most actions with the roll of a 20-sided plus appropriate modifiers. 3E expanded the combat system; introduced new character options, like the sorcerer class, and prestige classes, which can only be acquired at higher character levels and if prerequisites are met; removed previous restrictions on class and race combinations, and on the level advancement of non-humans; and allowed further customization with skills and feats. (wikipedia.org)