Feats are an innovation in the d20 system, breaking down some of the old class characteristics into special abilities that any character with the right qualifications can learn. They represent a person's capacity for great accomplishments, and are one of the most powerful tools for customizing a character. Fighters are no longer a tired hack-and-slashing stereotype and wizards are not restricted to the strict formulae of spell descriptions, with a careful acquisition of feats, the fighter can choose to be a force to be reckoned with in mounted combat or a canny combatant that takes any advantage in the battlefield, while a wizard con learn to make magic items or opt to manipulate the parameters of his spells.
A feat alters the way a character functions. The strongest barbarian will not deal the same amount of damage as a weaker one who knows Power Attack and Weapon Focus, and whose rage may last longer and give greater benefits. In the same way, the most dexterous rogue cannot position himself in the battlefield as advantageously as one with the Dodge and Mobility feats, not to mention the one who knows new and creative ways in which to use his sneak attacks. Feats introduce variants and innovation to the characters' features, and a chance for a player to come closer to the concept he had in mind when creating him or her.
This book classifies feats in five broad categories depending on the purposes they serve, and with some of them overlapping a little. Feats of the Arcane are all those special abilities that let arcane spellcasters increase their power, or grant them new sources of power. Included here are specific metamagic feats that are only available to arcane spellcasters. Feats of Arms, as the name implies, includes all the special abilities that influence violent conflict, from the training necessary to wield weapons and don armor and ways to do it better, to special offensive and defensive moves the character can perform during an encounter. Feats of Blood are race-specific feats, solely available to members of a particular race that enhance or diminish features of their blood.
Feats of Crafting are all those feats concerned with the creation of magical items. Feats of the Divine comprises those feats aimed at divine spellcasters, whether clerics, druids or paladins. Feats of the Mind stand on their own as ways to expand psionic capabilities, from a more accurate control of psionic powers and forging psionic items to special talents unique to those who use the power of the mind. It also includes those item creation feats specifically for the creation of psionic items. Feats of the Monstrous is made up of those feats that are aimed at creatures, as opposed to player characters or non-player characters.
Feats of Power are Metamagic feats, excepting those that are solely available to arcane, or divine casters, it is therefore the more general metamagic feats, available to any spellcaster. Feats of skill is a catch-all chapter, containing all those feats that are not specifically found in one of the other chapters, most noticeably feats intended to improve skills or non-specific spellcasting abilities of a character. Feats of Song and Stealth comprises the feats aimed at bards or rogue-type characters, whether the improving of a bard's song abilities, or the stealth and versatility of a rogue. Feats of Today and the Future is made up of a selection of feats intended for modern-day roleplaying in the d20 system. Feats of the Unliving comprises feats, and accompanying rules, intended for necromancers and those who deal with the undead.