Definition of a Music Video

• A music video is a short film or theatrical production that accompanies a complete piece of music or song.
• Modern music videos are primarily made and used as a marketing device. Their intention is to promote the sale of music recordings and sell more copies of the song.
• Although the origins of music videos go back much further, they came into their own in the 1980s, when MTV (Music Television)'s format was based around them.
• Music videos are often called promo videos or promos, because they are usually promotional devices.
•  Sometimes, music videos are termed short-form music videos to distinguish them from full length movies pertaining to music. 
• Music videos can accommodate all styles of filmmaking, including animation, live action films, documentaries, and non-narrative, abstract film.

http://en.wikipedia.org/wiki/Music_video