Disc jockey
A disc jockey, also known as DJ, is a person who selects and plays recorded music for an audience. Originally, "disc" (sometimes spelled "disk", although this is now uncommon) referred to phonograph
The phonograph record player, or gramophone is a device introduced in 1877 that has had continued common use for reproducing sound recordings, although when first developed, the phonograph was used to both record and reproduce sounds...

 records, not the later Compact Disc
Compact Disc
The Compact Disc is an optical disc used to store digital data. It was originally developed to store and playback sound recordings exclusively, but later expanded to encompass data storage , write-once audio and data storage , rewritable media , Video Compact Discs , Super Video Compact Discs ,...

s. Today, the term includes all forms of music playback, no matter the medium.

There are several types of disc jockeys. Radio DJs or radio personalities
Radio personality
A radio personality is a person with an on-air position in radio broadcasting. A radio personality can be someone who introduces and discusses various genres of music, hosts a talk radio show that may take calls from listeners, or someone whose primary responsibility is to give news, weather,...

 introduce and play music that is broadcast on AM
AM broadcasting
AM broadcasting is the process of radio broadcasting using amplitude modulation. AM was the first method of impressing sound on a radio signal and is still widely used today. Commercial and public AM broadcasting is carried out in the medium wave band world wide, and on long wave and short wave...

, FM
FM broadcasting
FM broadcasting is a broadcasting technology pioneered by Edwin Howard Armstrong which uses frequency modulation to provide high-fidelity sound over broadcast radio. The term "FM band" describes the "frequency band in which FM is used for broadcasting"...

, shortwave
Shortwave radio refers to the upper MF and all of the HF portion of the radio spectrum, between 1,800–30,000 kHz. Shortwave radio received its name because the wavelengths in this band are shorter than 200 m which marked the original upper limit of the medium frequency band first used...

, digital
Digital radio
Digital radio has several meanings:1. Today the most common meaning is digital radio broadcasting technologies, such as the digital audio broadcasting system, also known as Eureka 147. In these systems, the analog audio signal is digitized into zeros and ones, compressed using formats such as...

, or internet radio
Internet radio
Internet radio is an audio service transmitted via the Internet...