For Chorus you could also say "Repeated section". The first and second numbers specify the first and last bar of a section to be repeated. So you could have say, a 16 bar verse/intro then a 32 bar repeated "Chorus" and another 16 bar ending. To do this you would set the first and second numbers to 17 & 48 and the third to the number of repeats. Then enter the chords for all 64 bars (16 in, 32 repeated, 16 out). Then in the song settings menu specify a tag that starts at bar 49 and ends at bar 64 to get the 16 bars at the end.

There are ways to do even more complicated things, but you should get familiar with this first. Then come back and ask more questions (or read the manual :^)

Andy