What is a playback singer?

[Thunder Bulb]

Basically the the title, what is a playback singer?

 

[Odd Argument]

A playback singer is a vocalist who records songs for use in films, television, or other media, where actors or performers lip-sync to them. It is very popular in Bollywood movies.

 

[Reuben]

"A playback singer is a vocalist who records songs for movies, and the actors lip-sync to their voice on screen. They bring the music to life without appearing on camera themselves."