Chet,
Bouncing is just a way to get more trax out of what you're working with.
Let's say you're working with a 4 track.
Say you put the drums on Track 1, Bass on 2, rhythm on 3......


Then you mix, or bounce, those three trax onto track 4.

Now you've got channels 1-3 to add vocals, etc....

Let's say you put a lead vocal on 1, and a harmony vocal on 2.

Now you've got your original drums, bass, and guitar on 4.
You've got new material on 1 and 2....three is vacant.
You mix (bounce) tracks 4, 1 and 2 onto track 3......


etc.....