The difference in definition between "guts" and "balls"!
Guts - is arriving home late after a night out with the lads ,being assaulted by your wife with a broom, and having the guts to ask:
"Are you still cleaning, or are you flying somewhere?"
Balls - is coming home late after a night out with the lads, smelling of perfume and beer, lipstick on your collar, slapping your wife on the ass and having the balls to say:
"You're next fatty".