It is when you attack because you are the owner of the card. For instance, I could sacrifice a Pacifism enchanting your Elvish Mystic, as I am the owner and in control of the card. Hope that helps.
-Tim
Private Mod Note
():
Rollback Post to RevisionRollBack
Modern:
URB Grixis Delver URB
WUB Ad Nauseam WUB
(On Lantern Control)"A guy who literally just sits there and mills cards he doesn't like from your library while he slowly, slowly kills you this way."
"If a person's profile includes anime or My Little Pony, feel free to ignore everything they say."
-Tim