nice, is jazz the only genre you play?
no, I started out like most, learning rock songs and playing around with friends. Jazz is what you learn in school if you're not learning classical guitar. But I still listen to and play different things like rock, funk, bossa nova, and etc..
Nice job. I usually thought that Jazz has some kind of brass instrument like a trumpet or saxophone?
Well yes, usually you would hear brass in a jazz ensemble, but you don't need a horn to play Jazz. Jazz isn't defined by the instrument you use. Jazz is played on instruments from brass, woodwinds, guitar, bass, drums, etc... You can really play Jazz on any instrument. It just has to swing and there has to be improvisation (that's a very general classification, there is a lot more to it).