From the introduction:
A feat is essentially a highly developed super-skill, bestowing a permanent, non-magical, fixed ability usable at will. Feats represent a learned, trained, and experienced use of a physical, mental, or spiritual focus, granting an increased capability or function.
This new feature of the character generation/advancement process allows you to develop anything from a very specialized heroic character type to one with a wide array of heroic abilities and functions.
Bottom line: Feats help build the hero you become.