I could give you all of the standard definitions, but basically it is the art of using scale aircraft to do aerobatic dances.
There are certain routines that need to be done in each of the 5 classes. The higher the class the more difficult the routine.
You are judged against your peers to see who is the best in class.
ORIGINAL: mrlikescheese
What is IMAC? I've heard of it, but what is it?