5 string
He does not actually know how to play the banjo.
Banjo
In the film deliverance the banjo was played by Eric Weissberg and the guitar by Steve Mandell.
Dueling Banjos
"Dueling Banjos"
It is a comical reference to the movie "Deliverance" starring Burt Reynolds.
The banjo is classed as a string instrument
Asking for deliverance
A honeybear
Eric Weissberg performed the soundtrack for the movie. Billy Redden was the boy on the porch depicted as playing. The guitarist was Steve Mandell.
The BANJO was one of the instruments played on the movie soundtrack, and yes, it was played by Eric Weissberg: http://en.wikipedia.org/wiki/Dueling_Banjos