A slapstick film is a funny movie that makes people laugh by showing characters doing silly things like falling down, getting hit, or getting into wacky situations. It's all about physical comedy!
Think of it like when you and your friends run around and play and pretend to fall over and make silly faces. Except in a slapstick film, it's all planned out and there are actors who are getting paid to act silly.
One of the most famous slapstick films is "Home Alone". Remember how funny it was when the bad guys would try to catch Kevin and kept getting hurt? That's an example of slapstick comedy.
Slapstick films usually have exaggerated actions and reactions, so things that wouldn't normally be funny in real life (like getting hit with a pie in the face) become hilarious in the movie.
So, in simple terms, a slapstick film is a funny movie that makes people laugh by showing characters doing silly physical comedy.