Fan Fictions and Original Fictions.

Question: Are fan fictions not original?

Because I thought something was original as long as you make it yours?
But obviously if it contains any celebrity or band member, it's only natural that i'd tag it as a fan fiction..
Would it be right to tag it as fan fiction and original fiction?
A lot of people seem to do this, so I'm a bit confused.
I don't mind fan fiction as long as the story is well written and good.
But I am getting annoyed of all this fan fiction labeled as original fiction.
I feel like I'm contradicting myself.