A cleric's deity influences her alignment, what magic she can perform, her values, and how others see her. A cleric chooses two domains from among those belonging to her deity. A cleric can select an alignment domain (Chaos, Evil, Good, or Law) only if her alignment matches that domain. If a cleric is not devoted to a particular deity, she still selects two domains to represent her spiritual inclinations and abilities (subject to GM approval). The restriction on alignment domains still applies.
Each domain grants a number of domain powers, dependent upon the level of the cleric, as well as a number of bonus spells. A cleric gains one domain spell slot for each level of cleric spell she can cast, from 1st on up. Each day, a cleric can prepare one of the spells from her two domains in that slot. If a domain spell is not on the cleric spell list, a cleric can prepare it only in her domain spell slot. Domain spells cannot be used to cast spells spontaneously.
Subdomains—more specific focuses for clerical worship and power that allow players greater flexibility in customizing their characters. Every domain has a number of subdomains listed indented undernearth it. Each subdomain replaces a granted power and a number of spells in the domain’s granted spell list.
A cleric who chooses a subdomain must have access to both the domain and its subdomain from her deity. If a cleric selects a subdomain, she cannot select its Associated Domain as her other domain choice (in effect, the subdomain replaces its Associated Domain). Subdomains are treated as equivalent to their Associated Domain for any effect or prerequisite based on domains. If a subdomain has two (or more) Associated Domains, the cleric can only select the subdomain for one of her domains. Subdomains can be selected by druids (except the metal subdomain) and inquisitors (if their deity allows it).