Venom is a comic book with a complicated past.
He's a Marvel character who first appeared in Spider-Man stories. Now, hold on. The upcoming Venom movie isn't a Marvel movie. This is a holdover from the FOX portion of the Marvel library. Meaning the folks that made the X-Men and Deadpool movies made Venom. NOT the folks who made Iron Man and The Avengers.
As for the origins of the character, that's EVEN MORE complicated. CLICK HERE to read about the comic book origins of the Venom character.
Venom hits theaters this weekend.