A charade is something done just for show. Your devotion to vegetarianism would be a charade if you actually ate cheeseburgers when no one was looking.
When you want things to appear different than they really are, you might be tempted to put on a charade, like a charade of happiness when you are really feeling down. Charade is also the name for a silently-acted clue in the game called charades — which originally wasn't silent. It used indirect descriptions of the words; the non-speaking version was called dumb charades.