Unless you meant:
They are both places you go to watch movies and plays. Theater is the American English way to spell it. Theatre is the British English way to spell it.
Theater
Cancelling is the way you spell it in British English and Canceling is how you spell it in American English.Cancelling is the way you spell it in British English and Canceling is how you spell it in American English.Cancelling is the way you spell it in British English and Canceling is how you spell it in American English.Cancelling is the way you spell it in British English and Canceling is how you spell it in American English.Cancelling is the way you spell it in British English and Canceling is how you spell it in American English.Cancelling is the way you spell it in British English and Canceling is how you spell it in American English.Cancelling is the way you spell it in British English and Canceling is how you spell it in American English.Cancelling is the way you spell it in British English and Canceling is how you spell it in American English.Cancelling is the way you spell it in British English and Canceling is how you spell it in American English.Cancelling is the way you spell it in British English and Canceling is how you spell it in American English.Cancelling is the way you spell it in British English and Canceling is how you spell it in American English.
theater
Theatrum (genitive: theatri).
Theatre :)
People in the theatre world tend to spell it "theatre" and those who are not spell it "theater." The basic difference as it was explained to me by one of my theatre professors in college is: Theatre is the art form and Theater is the building. Example- I am going to the Kodak Theater to see a theatre performance. Also, theatre is the (British) English spelling of the word theater.
The theater art (a play in song) is "opera".
The British spell it "skilful".
British.
Theater becomes Theatre.Honor becomes Honour.Pajamas becomes Pyjamas.Skillful becomes Skilful.
The British spelling of favorable is favourable