Domains are broadly defined as divine concepts worthy of devotion, which is the source of all divine magic. Each deity is associated with one or more domains. Clerics, Druids and Inquisitors all get to choose domain(s).
Domain Summary Edit
The deities of clerics and inquisitors influences their alignment, what magic they can perform, their values, and how others see them. A cleric chooses two domains from among those belonging to her deity. Inquisitors and druids may select only one. Clerics and inquisitors can select an alignment domain (Chaos, Evil, Good, or Law) only if their alignment matches that domain.
Each domain grants a number of domain powers, dependent upon the level of the divine spellcaster, as well as a number of bonus spells. A divine spellcaster gains one domain spell slot (even clerics with two domains) for each spell level she can cast, from 1st on up. If a domain spell is not on the caster class' spell list, a caster can prepare it only in her domain spell slot. Domain spells cannot be used to cast spells spontaneously.
Unless otherwise noted, activating a domain power is a standard action.