I think most would probably agree all fittings that just change the direction of pipelines could be called "bends", of one sort or another.
I guess some of these folks might refer specifically to 90 degree bends as "el(l)s" (they look like an "L"?) or "elbows"; whereas, a few other folks might even call all angle bends including 90 degree "elbows". Incidentally, I have heard in effect special 180 degree bends also called "return" bends in the past, for perhaps obvious reasons.
I'm not sure where all formal authorities lie on all this, but I believe at least some ISO and ANSI/AWWA specifications, at least for water pipe fittings, prefer specifying the specific degree angle and then only the term perhaps least likely to be confused (i.e. "bend"). Thus, a 90 degree "ell" (perhaps to some) becomes per the standard a "90 (degree) bend", and I'll bet most get the fitting then they want with this standard convention!