Back when I played WoW, my dad would often ask what is was about.
I tried to explain it to him.
It really puzzled him why my character ran around without stopping for a breather and why I killed creatures.
This happened once:
"Why does he have teeth poking out of his chin?"
"Cause, he's a troll. Trolls have tusks in this game"
"Why is he running?"
"There is this quest *opens map* I have to run all the way down there"
"...It's not YOU running, you know..."
"Uuh, yes, I know that it's not me..."
My sister was really worried that I would get addicted, just because I was playing for 20 minutes or so on christmas eve.
My mom often calls my ds a "computer game"
Other than that, they don't care much about video-games. They just roll with it since it's my thing, I guess.