What is movement improvisation?

I am a young actress and am looking to audition at a local theatre near my home. On their website it says that at auditions we must do a movement improvisation and recite a monologue, but gives no other description. I know what a monologue is but not movement improvisation! I need help because my biggest dream is to be an actress and I really think that this audition could really get me headed in the right direction! Thank you! :)