A pantomime is a play ussually done at a local theatre near christmas time. Ussually a princess story like cinderella or peter pan. It can go wrong and it doesn't really matter. The ussually get the audience involved and it's more for kids. Also a panto is where they don't use a song to tell the stroy. They might use a pop song and ussually has background dancers and men dressed as ugly women and silly characters. The audience sometimes answers the questions like "Oh no your not!" or "He's behind you!"
A musical is a play that is ussually in the West End or a proffesinal theatre that goes on all year round. They tell the stroy through a song.
I hope this helped you!