Crunch

Crunch is roleplaying gamer slang for the actual game mechanics of a system or setting; it is the opposite of fluff, which describes things in an in-universe sense. For example, a special ability or feat's fluff might say that "You grew up in a school for mages, and have thus learned some of the rudiments of magic"; the associated crunch could be a +2 bonus to Spellcraft and Use Magical Device checks.

One of the traditional failings of powergamers is a focus on crunch to the exclusion of the fluff, creating characters that are mechanically powerful but make little sense from an in-character perspective.