What exactly *is* gelatin? What's it made of?

When I was on Atkins, I used to eat a lot of
Sugar-Free Jello (especially with whipped
cream or cream cheese or cottage cheese.
Eeeps! No wonder I was so messed up and
gained weight!) but gave it up when I realized
I was having physical reactions to NutraSweet.
(This was before I figured out the dairy part).
Instead I bought a lot of unflavored Knox and
used extracts. I still have quite a few boxes
left.

If it's illegal, I'll give all my Knox away. If it's
legal, does anyone have any ideas what I can
do with it?

Btw, I too am wondering about Stevia. Ray?

Vickie