The skill tree is an [[interface]] window in which all of the skills available to each class are displayed. When a character in Diablo III gains a level (or possibly earns a skill point from a [[quest]] reward), it can be placed into one of the [[skills]] in the skill tree, thus enabling or upgrading that ability. [[Respecs]] will be available to change skill points after after they're placed, and [[runestones]] can be socketed into skills, greatly modifying their forms.

[[Respecs]] will be available to change skill points after after they're placed, and [[runestones]] can be socketed into skills, greatly modifying their forms. The forms of the skill trees in Diablo III have evolved radically during the game's development. The current form has no [[passiveskills]] skills in the skill trees, just [[activeskills]] skills, and the trees are not divided into sub-trees; all skills are arrayed in a sort of menu, allowing each class to mix and match freely between them.