What is the broken part called and is it necessary?

I hit a snowbank head-on at about 15 MPH with my 2002 Saturn and though the bumper cover appears OK, on the lower front where there are two large oval openings the black plastic in there is broken. Is this what is the bumper filler and cosmetic or is a necessary reinforcement?

Can you show us a photo?

Sounds like a air duct,you should either repair as designed or get creative with tape and such,you need to maintain the ability for air to be directed as designed.

fog light locations?

Here you go.

And another shot.

Try as I may I cannot see a crack there.

The first photo shows the fog lamp location at the far right (outside corner).

I think this is just a air flow opening to direct air through the rad.

It is hard to see, but inside the black plastic is missing a chunk–you mya be right that ti is an airflow opening.

Just be aware that your A/C condensor, or your radiator, or your transmission cooler could be immediately behind that broken plastic part. The part itself is essentially non-functional, but on the chance that something behind it could have been damaged, it would be a good idea to have a mechanic check that area.