A disc jockey, disk jockey or DJ is a person who selects and plays prerecorded music for listeners.

Many DJs also speak to the audience, either to give the names of the songs, a reggae disc jockey (deejay) is a vocalist who raps, toasts, or chats over pre-recorded rhythm tracks; and mobile disc jockeys travel with mobile sound systems and play from an extensive collection of pre-recorded music.

Mobile Disc Jockeys are an extension of the original Radio disc jockeys. They travel with or go on tour with mobile sound systems and play from an extensive collection of pre-recorded content for a specific audience. Today there are a variety of Mobile Disc Jockey business models, including full-time, part-time, multi-operator, and single-operator companies. Mobile DJ should be able to play a client’s specific requests by incorporating them into a repertoire of party favorites (this is called "reading" the crowd).

In the 2000s, mobile DJs need a large selection of music, professional-grade equipment, good organizational skills, vocal talent as an MC, mixing skills, quality lighting, insurance for liability, and on-site back-up equipment.

In the 2000s, the role of the Mobile DJ has expanded. Many Mobile DJs have assumed additional responsibilities to ensure an event's success.

These responsibilities include the roles of MC, event organizer and coordinator, lighting director, and/or sound engineer.

The word hotel derives from the French hôtel, which referred to a French version of a townhouse or any other building seeing frequent visitors, not a place offering accommodation.