He drowned at Camp Crystal Lake, then his mommy took revenge on the camp councilers, then his mother got killed and now he revenges his mother by killing everyone that comes to Camp Crystal Lake also known as Camp Blood.
He has appeared in 11 movies by now because even if he gets killed he just keeps coming back.
A little bit of history:
It was thought that Jason Voorhees had drowned in Crystal Lake when he was 11 years old, because the coucelers weren't paying attention.
A year after that on Friday the 13th two councilers were murdered
The camp got closed but was reopened after a couple of years (On a Friday the 13th)
The killings started again and it was soon clear that Jason's mother, Pamela Voorhees, was the murderer.
She took revenge on the coucilers because they didn't pay attention to her child.
The only survivor, Alice, decapitated Pamela.
Jason saw his mother being decapitated and took revenge on everyone who came back to Camp Crystal Lake, he even went down to Manhatten once and he also went into outer space.
Jason first appeared in the end of Friday the 13th as a deformed half rotting kid that jumped out of the water, this was actually a dream of Alice.
Then he appeared with a brown sack on his head and after that with the hocky mask wich is now pretty much his trademark.
Jason never really runs, but strangely he always manages to keep up with his victims and always manages to get to the hidingplace of the teens before the teens themselves.
The teens always appear to be very stupid in the movies (besides some eceptions)
Stupid teenager examples:
1. The woods are scary, let's go in!
2. All our friends have mysteriously dissapeared, let's have sex!
Oh yeah and Jason never dies, he just keeps coming back and because of that the movie people keep making sequels.
Jason was also resurrected by Freddy Krueger to scare the kids on Elm Street so they would believe in Freddy again.
But Jason just couldn't stop killing the teens on Elm Street, because of this Freddy got mad and decided to take care of Jason himself and thus started the showdown between two great slasher icons.
FUNNY FACT: Whenever people start to have sex in the movies, Jason starts killing.
"itz like a jason voorhees copycat!!!!!!!"