...I say that with great affection.
Generally, when people discuss LARPing, the game is fantasy or science fiction based. I think one could argue that historical reenactments are also LARPing, since both groups refuse to break character and get on my nerves. (Also said with great affection!)
LARPing is popular at comic conventions, where people are known for dressing up as famous comic or pop culture characters. LARPing was part of the plot of the film Role Models. These clips should help you out:
Live action role-playing game, Wikipedia
How LARP Works, How Stuff Works