Hello Tim. banjohangout.com has lots of info. 5-strings are largely used for bluegrass, old time and folk music, four-string for Dixieland jazz or traditional music , like Irish and six-strings are for guitar players. These are starting points and any type of banjo can go about anywhere it wants to. The orchestra ( real, not Muppet ) on the old " Muppet Show " featured tenor (4-string) banjo prominently although it wasn't Dixieland.
Yours,
SKP