DJing is the act of playing and performing music for a concert/venue while using instruments to create different sound with effect. It requires mixing, effects, rhythm, audio engineering, and sometimes MPC's (some MPC users are considered to be 'DJ's' all though the term means Disc Jockey). The role of the DJ is to deliver the music in the best way possible and the coolest way possible. It is also sometimes the DJ's role to be the Host of the party/venue. Hope that helped a little, if you want specific's just search up the term Disc Jockey.