Differences-
1. Theatre is live. Film has been captured in the past. We only see after the making process is done.
2.You have chance for improvement in each theatre shows but its impossible in Films. Once film is done its done.
3.Normally Theatre is cheaper, films are costly.
Similarities-
1.Theatre and films both are arts, so many varieties of arts melt into theatre or film to make it happen.
2.Theatre and films both are very effective medium of communication.
3.Theatre and films both are considered as great form of Entertainment.