The way that the term codec is generally used makes understanding what one actually is a bit confusing. Most people have the general impression that a codec is somehow related to both software and files. Maybe you have run across the term when you find out your computer doesn’t have the codec you need to play an audio or video file back, or maybe you have heard it referred to as a method to store data inside of a file or wrapper. Beyond that the details are sketchy for most people. The purpose of this paper is to clarify what a codec is, how it is used and what that means to archives.