More info about the FAQ can be found at the bottom of this paper. All three share the common goal of providing an entertainment for a wide variety of people through various means, mostly however, through music. A DJ's job is to combine all the elements necessary for their performance into one fluid package which can be easily swallowed by all of his or her's listeners. For some DJs this includes talk and games, while for others it means spinning the latest and greatest to the hippest people in town. All DJs, however, deserve respect for the job they do.
Mobile DJs are the most common.
This sort of work usually entails entertaining a wide array of tastes and age groups, as well as a bit of MC'ing. Radio DJs are the least common. Their task is to make sure there is never any dead air time by filling it with either their words, or music. Again, there is a certain mass appeal that needs to be worked on and being a Mr. Personality is important. Club DJs can be found, but aren't nearly as prominent at mobile DJs.