google, numb nuts (pun intended'ish)

Well little Jimmy, I'll tell you. T-Bagging as it is often worded is where (usually in FPS (First Person Shooter) Game) you take your genitalia and squat up and down reapetedly upon an unconcisous or dead persons face, showing that you have just served him/her.
P.S. Sorry for bad grammar.

A Tea Bag is when a girl has her mouth open and you dip and raise your testicles (t-bag) in her mouth like making a cup of tea. So for the rest of us who actually get out of the house its possible to do without a video game character. Use this knowledge wisely my son.