unrelenting - relentless

How do y'all understand the difference?

theatre - theater

I know the first is Brit spelling; the second, American. But I see "theatre" all over the place here in USn's land. One theater-type told me it's to distinguish "theatre" the art from "theater" the venue, but I dunno. I see "Theatre" as part of a venue name all the time. Is it just that it looks better, more consmopolitan, or something?