I have a VW Jetta 2001. There is this rubber lining that seems to
cover the wheel well. Unfotunatly, I hit one of those cement parking
blocks a little to hard and it didn't break the bumper but it forced
that wheel well cover to pop out. The screws are still in there but
they seem to attach to the side panel and they ripped through the
screw holes on the side pannel. So I assume to reattach this cover
piece I would have to get a new bumper and side panel as well as the
wheel well cover.

What is the purpose of this and does this cover have a special name?
Is it really worth having it fixed? Is it just to keep mud and water
from shotting up and rusting underneath?

thanks.

Yep, suppose also helps silence the road noise from the tyre (tire) a bit
too. Also I wouldn't want stones going up in there and chipping the
protective paint that actually stops the rusting in the first place. May
find it will start to rust with all the stones whacking up inside there.