In US English, a slipper is a bedroom/house shoe that dogs are reputed to chew on. A flip-flop is day wear, outdoor, beach, etc. At least in my part of the US! And just to make it complicated, some people call slippers "house shoes."
(And thanks, the slipper I thought of was my chewed flip flop. The other slippers are pantoffels around here. Beautiful word even though I never use pantoffels.)