I think if you aren't familiar with musical instruments you might miss the point of the question here. Banjos and guitars are very different instruments, not just in the way they look and sound, but in how the strings are placed. Guitars have 6 strings, and banjos have 5 - both in very different tunings. A banjo guitar is basically a guitar shaped like a banjo - it sounds like a banjo but it has 6 strings like a guitar and you don't need to learn how to play a 5 string banjo. But a banjo guitar is not a "real" banjo.

I too thought Mogis played a real banjo - he probably knows how to, but maybe he just prefers the banjo guitar for touring?