I think there are two types, there is "Graphetti" (Sorry I'm tired) and then there is Spray Art.
Difference? Grafetti, that trash people put up that looks like shit and was just a waste of time that noone should look at. This stuff makes the place look terrible.
Spray Art, the hard works of art that people risk fines and incarceration to do and spread to the world to see for no money at all. There is a certain honor to these peices, I wish I could talk to them but that's impossible...
Anyway this is a peice near my Highschool that I like, I didn't do it but it's nice. There is another half to it, same word but I couldn't get it from the angle...