What is a "One-Off", "Master CD", or "Gold Master"?

All of these terms mean the same thing. It is just a difference in the terminology an individual prefers to use. They all are nothing more than a CD-Recordable which contains the final version of the information to be replicated. This is what we start the replication process from.

What does the term "Glass Mastering" mean?

Glass Mastering is the first part of the process needed to actually make the "metal stamper" that is actually put into the injection molding machine to produce the CD-ROM's. The first part of the process is to convert the data into the actual highs and lows. These are actually done on a piece of glass. From that point the process continues and eventually the metal stamper is made. The glass master is destroyed during the production of the nickel stamper.