Usually charts have sections A B C D. Although new charts sometimes have the letter in a square, all the people I know talk about it as circles. So at circle C...

Basically if you have the chart and watch you will see that they often just take a section, and do that part over and over, jumping in and out. If you have not worked together before there are a few visual cues as to where to go, like tapping your head to go back to the top or redo something.

A solo can be as few as a couple of bars though. Don't get hung up on the term.

John Conley
Musica est vita