A one-time magical effect. The two primary categories of spells are arcane and divine. Clerics, druids, paladins, and rangers cast divine spells, while wizards, sorcerers, and bards cast arcane spells. Spells are further grouped into eight schools of magic.
Sometimes a creature can cast arcane or divine spells just as a member of a spellcasting class can (and can activate magic items accordingly). Such creatures are subject to the same spellcasting rules that characters are, except as follows.
A spellcasting creature that lacks hands or arms can provide any somatic component a spell might require by moving its body. Such a creature also does need material components for its spells. The creature can cast the spell by either touching the required component (but not if the component is in another creature's possession) or having the required component on its person. Sometimes spellcasting creatures utilize the Eschew Materials feat to avoid fussing with noncostly components.
A spellcasting creature is not actually a member of a class unless its entry says so, and it does not gain any class abilities. For example, a creature that casts arcane spells as a sorcerer cannot acquire a familiar. A creature with access to cleric spells must prepare them in the normal manner and receives domain spells if noted, but it does not receive domain granted powers unless it has at least one level in the cleric class.