I can tell you a few of the meanings
Pokemon Games
RBY=Red, Blue, Yellow
GSC=Gold, Silver, Crystal
DPP=Diamond, Pearl, Platinum
SS= SoulSilver
BW= Black, White
Smogon Tiers
OU=Overused
RU=Rarely used
NU=Neverused
NFE=Not Fully Evolved
LC=Little Cup
Others
BP=Battle Points/Base Power
BST=Base Stat Total
VGC=Video Game Championship
NVE=Not very effective
I don't have all of them, but at least you know some of the meanings. (-o-)