How to explain "simulationism"

I think I've mentioned before that my wife runs a campaign on the same
evening that I do, with a different set of players.  Her campaign,
while not as "simulationist" or world oriented as mine, is still
pretty strongly toward that apex of the triangle.  The main difference
is that she doesn't enforce world consequences on the player
characters as strictly as I do.

One of her players seems fairly strongly in the "story" camp - her
discussions assume that roleplaying games are fundamentally narrative
in nature, and she assumes that the gamesmaster derives pleasure from
the game in essentially the same way as the players do.  This clash in
assumptions about what roleplaying games are is leading to problems -
especially since the player in question really doesn't seem to
understand what a simulationist style is all about.

Any suggestions on how to explain the issues here?  If Russell Wallace
or some of the other people with somewhat dramatist preferences is
still around, I'd especially appreciate your input, but any
suggestions are welcome.