This is a song by tupac released in 1996 or something. Since I listen to a lot of american rap, I see that the word Shorty appears many times in rap songs... I'm not actually sure about its meaning. A shorty is it a kind of thug or bad boy?
If you like rap, I suggest you familiarize yourself with urbandictionary.com.
Originally used to mean a young man, new to the game. By new to the game, I don't mean he just meant a rapper, but he just started selling crack, just started rapping, whatever, but even simpler it was a term used to mean just a person much younger than you.