A.B., IMHO the best thing to do is to explain it this way:
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It is a pen and paper game, where you write up a character to portray, as in a story, and you have rules that describe what the character can and cannot do. What he can do is defined by the genre of the story - medieval fantasy, or sci-fi, spy thrillers, or "mad max" future apocalypse, or whatever genre you can imagine.
It's fun because you can spend time with friends, you have fun creating a group story, and for some people it's fun to add combat and strategy elements to the game.
One person acts as a referee, and this person describes situations and challenges to the other players so their characters can act and react to them. He also arbitrates any rules of the game that need it.
And MOST IMPORTANTLY - you can learn more about it by participating in it than in hearing it described.
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That ought to be enough introduction to someone who knows nothing about it. Everyone knows what a character in a play is, everyone knows what a referee does in a game, and everyone understands spending time with friends.
P.S. - I am pretty sure Snoweel was pulling your chain - he has been around these boards long enough to know both you and your back story.
***Kind of reminds me of that cheesy TV movie about Sherlock Holmes in the 20th century that came out in the 1980's. Watson's great-great-great granddaughter finds Holmes and thaws him out.
"So Watson, why did you never marry?"
"I was married. Once. For 6 GLORIOUS months. Until my husband ran out on me."
"I see. Another woman, no doubt."
"It wasn't a woman."
(long pause) (look of confusion, followed by shock) (gets back to work)***