Rather than trying to explain what LARP is, I'm going to turn it over to YouTube, which already has a number of videos on the subject. It would be nice to add to this with my own videos, but that's for the future, I think.
The first is a documentary trying to ask what is LARP?
But that's not quite the kind of LARP I will be running.
I found this link, which is for a trilogy of Vampire: The Masquerade games. The cool thing about it is that the GM is explaining things as they go along, so hopefully it should make more sense to non-gamers.
Here is a more interesting one, but sadly only if you can comprehend German.
And, lastly, here are two videos from Kettle of Fish Production's Fading Suns convention LARPs.