The main difference between a DJ and a producer is that a DJ takes already created music and mixes it. A DJ may use special effects, looping, and other techniques to change the sound or structure of a track. A producer creates the music in a studio using a Digital Audio Workstation. Such programs include logic and pro tools.
They produce their original works and also remix other produced tracks when they are furnished with remix stems. Once a track is finished, a producer sends it to a label to be sold commercially. Many DJ's are producers, and many producers are DJ's. The critical difference is that a producer creates music in a studio and a DJ takes already created music, and he mixes it.