Here you can have a good natured fight with a buddy or enemy of yours without having to worry whether or not it will affect your character in RP or not. Think of it as a practice fight, so even if your character dies in the fight, it won't die in actual RP.
Here you can RP out something that happened in you character's past, something that would've affected your character greatly, or maybe you can even just RP you character buying a new pair of shoes from twenty years ago. It depends on you, really.