A production is a recording of a song
A production is an alternative recording of a composition (i.e. a master). It can be a different form of the same song, for example, a remix, acoustic, or live version.
An example of a production is the 2017 live recording of Mozart’s Requiem by the Orchestre national de France. Another example is Nirvana’s acoustic version of “About a Girl” on their 1994 album MTV Unplugged in New York.