Changes

Diablo III skills are either "active" or "passive." There are many more passive skills than active skills. At Blizzcon in October 2008 (a very preliminary build of the game), each skill tree was set up in tiers, with 4 or 5 skills per tier. One On each tier, one or two were active and the rest were passive, on each tier. Thus there were many more passive than active skills.

Active skills are used by clicking their icon, and are generally direct attacks; things like [[Spirit_Skill_Tree#Soul_Harvest|Soul Harvest]], [[Battlemaster_Skill_Tree#Hammer_of_the_Ancients|Hammer of the Ancients]], or [[Arcane_Skill_Tree#Magic_Missile|Magic Missile]]. Active skills attack, or cast a protective armor, or stun monsters, etc.  Passive skills grant the characterr some sort of bonus that is always in effect. Passive skills do not need to be cast to activate them; they give a bonus all the time, as soon as points are placed into them. These are skills and spells like [[Arcane_Skill_Tree#Efficient_Magics|Efficient Magics]] or [[Battlemaster_Skill_Tree#Power_of_the_Battlemaster|Power of the Battlemaster]]. (No passive Witch Doctor skills have yet been named.) Passive skills boost the damage of other spells, or or lower the mana cost of casting them, or increase their duration, etc. Passive skills were often called "masteries" in Diablo II, and that term is still applicable to many of them in Diablo III.