G.13.1- To "destroy" a permanent (see Rule K.19) is to place it into its owner's graveyard from play. [CompRules 1999/04/23]
G.13.2- A creature can regenerate (see Rule G.29) if it is destroyed. [CompRules 1999/04/23]
Note- Destroying a permanent is just one way to put it into the graveyard. There are other ways which do not count as destroying the permanent.