Here are the definitions from their rulebook located here: Smash Up Rules
Discard: When a card gets discarded, it goes to the discard pile of the player whose deck it came from, no matter who played or controlled it.
Destroy: When a card says to destroy another card, put the destroyed card in its owner’s discard pile.
If I can destroy one of my minions to draw the same number of cards as its power, would I be able to destroy one from my hand? I'm thinking no, but would like to appeal to others who may have broader experience with other games that might use this terminology commonly or might simply know a ruling on this.