What happens if I didn't finish all of my antibiotics?

It depends. Many people stop taking antibiotics after they feel better. For some infections, that may be ok. There are other infections that if you don't take the full course of treatment, the infection may come back, and may be worse or harder to treat the second time around. If you are feeling better and wonder if it's ok to stop the rest of your antibiotics, it's best to ask your doctor.
Antibiotics. So long as you took enough to eliminate the infection, that is all that is required.