When trying to explain it to the uninitiated, I have always described role 
playing games as "Let's pretend for grownups".    If pressed further, I 
will talk about it as an interactive storytelling experience.  One person 
is the producer/author (GM), who creates the imaginary environment (the 
sets) and portrays everyone the players meet in the personae of their 
characters.  Instead of following a script, however, the actors (players) 
are improvising, based upon the parameters set out for their characters.

I don't know that this is what you're looking for, but you're welcome to 
use or adapt it.

Jae Walker

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