Hello Katya, It should be "fout" not "fou". "fou" means "crazy". "fout" comes from the verb "foutre" and it simply means "to do" in that case. It's generally used when the speaker is angry. Qu'est-ce qu'elle fout ? = Qu'est-ce qu'elle fait ? = What is she doing? It can also be used when someone screwed up something. OMG qu'est-ce que t'as foutu ? = OMG qu'est-ce que t'as fait ? = OMG what have you done? It can also mean "mettre" when you're looking for something you can't find (at home, in your bag, ...) Où j'ai foutu mes clefs ? = Où j'ai mis mes clefs ? = Where did I put my keys? The pronominal verb "s'en foutre" means "to not care". Non mais je m'en fous en fait. = Yeah but I actually don't care.