Not too mention the various unofficial abbreviations(generally Qantas specific) you may see on this (and other) boards:
QP = Qantas Pub, more commonly known as Qantas Club (or QC)
QC = Quickcheck, not to be confused with QP (although sometimes it is)
SC = Status Credit
UC = Upgrade Credit
N class = usually lowest domestic fare, commonly known as "red-e-deal"
MR = Mileage Run, where individuals pay money to fly around with sole purpose of accumulating SC's and sometimes miles as well, or route their SYD to MEL fare via Kalamazoo and Timbuktu to pick up extra SC's.
QF, DJ, JQ, NZ are all airline designators (Qantas, Virgin Blue, Jetstar, Air NZ), with a comprehensive listing at
Amadeus.
Also (although someone else can probably shed some light on what the actual acronyms mean), the following refer to Qantas status:
WP = Platinum
SG = Gold
PS = Silver
NB = Bronze