Music production is the process by which music is created. From the very beginning forming in the artist mind to the moment when the listener has a new track on their playlist. 

Production music libraries license their copyrighted music for use in film, television, and radio productions. 

A remix is a piece of media that has been altered or contorted from its original state by adding, removing, or changing pieces of the item. It's all about changing the original material to create something new.

Mixing is a process of optimizing and combining multitrack recordings into a final mono, stereo, or surround product. Mastering, on the other hand, is the process of preparing and transferring recorded audio from a source containing the final mix to a data storage device (the master), the source from which all copies will be produced.