Yo Hopper of Grazza:
Mastering? Well, you take all of your tracks, send them to a studio or use your studio, set all the levels, set all the reverb, set all of the eq's, set everything, and mix it down to CD? Tape?
ADAT?
Whatever.
If you have a solid copy and it suits your ears, you can use it as a Master to create more CD's, etc.
Green Hornet