Theatre and Theater

Theatre and Theater
 

I am confused about these two words...they have the same meaning and are the same words (except for the spelling of course) but what confuses me is that I though the British uses theatre and Americans use theater.
I watched Jeopardy today and the final Jeopardy clue category was Muscial Theatre.

The British use theatre as a rule. We use theater in the U.S., but every now and then we like to spell it the other way, especially when we want to instill wonder or intrigue. There's a certain amount of elegance when we use quaint words.

Which would you rather visit? ...
Ye Olde Candie Shoppe, Towne Centre -or-
The Old Candy Shop, Town Center

ah I see....and I also see Center and Centre too