SRD:About Feats

Prerequisites
Some feats have prerequisites. Your character must have the indicated ability score, class feature, feat, skill, base attack bonus, or other quality designated in order to select or use that feat. A character can gain a feat at the same level at which he or she gains the prerequisite.

A character can’t use a feat if he or she has lost a prerequisite.

Types of Feats
Some feats are general, meaning that no special rules govern them as a group. Others are item creation feats, which allow spellcasters to create magic items of all sorts. A metamagic feat lets a spellcaster prepare and cast a spell with greater effect, albeit as if the spell were a higher spell level than it actually is.

Feat Descriptions
Here is the format for feat descriptions.

Prerequisite
A minimum ability score, another feat or feats, a minimum base attack bonus, a minimum number of ranks in one or more skills, or a class level that a character must have in order to acquire this feat. This entry is absent if a feat has no prerequisite. A feat may have more than one prerequisite.

Benefit
What the feat enables the character (“you” in the feat description) to do. If a character has the same feat more than once, its benefits do not stack unless indicated otherwise in the description. In general, having a feat twice is the same as having it once.

Normal
What a character who does not have this feat is limited to or restricted from doing. If not having the feat causes no particular drawback, this entry is absent.

Special
Additional facts about the feat that may be helpful when you decide whether to acquire the feat.