What does "Master" mean?

[PenguinHead]

Demos...Outakes...Unreleased Versions...Alternate Versions...Remixes...Masters....while some of these terms seem obvious to me...it appears that there is a wide range of interpretation as to what these mean...and they apparently mean very different things to different people. Adding to the confusion: when someone deems a particular song with a particular term...it gets perpetuated throughout the fan base...whether or not it's the most accurate term.

What accurately constitutes a "master?" I think this term is most often misused.

What is confused collecter to do???