Short for disc jockey, a DJ (in the broadest sense) is any individual that utilizes pre-recorded media for the entertainment of others. In more specific terms, there are several different types of DJs, each fitting into a particular niche and capable of being described in different ways depending on: (1) where the DJ plays from (e.g., from a radio broadcast booth or in a nightclub), (2) who the DJ plays to (e.g., to the general public or to the students at a high school dance), (3) what type(s) of music is being played, (4) how the music is played (e.g., songs played end-to-end from compact discs or mixed from vinyl records), and the motivation behind song selection (e.g., listener requests or something more artistic). Regardless of their differences, the unifying factor that seems to make any one DJ a DJ is that s|he is ultimately responsible for the music being played. When DJs work for a media company their selection of music and content may be constrained for reasons of taste, local law and/or advertisers' preferences.
As a verb, "to DJ" is regarded as the act of mixing songs in any given order (again, regardless of whether they are mixed end-to-end or in a concurrent, layered fashion). However, in some circles, to use "DJ" as a verb implies that the disc jockey will perform a series of mixes in succession over a period of time in which the songs gain emphasis from each other to provide a more dramatic, perhaps more holistic, musical experience.
THE DJ AS AN ARTIST
A recent phenomenon in the musical community (but primarily within the sphere of popular music) is the assertion that some DJs are not simply "playing records" but are in fact creating new music out of the playback and mixing of the pre-recorded media. Fuelled mainly by the innovative mixing techniques that have come out of the hip hop and EDM scenes, and regarded as a musical extension of the literary cut-up technique, this growing attitude posits that such a DJ is not content simply to beatmatch two or three records and layer them over each other but that the end product should emerge as a new musical composition. To achieve this goal, such a DJ may employ such techniques as phrasing, sampling, scratching, the application of effects (e.g., delay, flange, etc.), and any other technique the DJ feels inclined to use. Examples of such DJs as "artists" adding musical or dramatic value include Coldcut and DJ Spooky. In effect they are developing an aural montage that may be spontaneous/improvised or carefully crafted. There are parallels in surrealism and the visual arts.