what is the difference between carnage and venom?

Well, Venom is the original and possessed Peter Parker. After Peter rejected the Venom symbiote, it bonded with Peter's high school nemesis Flash Thompson and became obsessed with killing Peter, however, he eventually becomes a hero. Meanwhile, Carnage is an offspring of Venom permanently bonded to the psychopath Cletus Kasaday who just likes to kill.

MagicianTrent is pretty spot-on, but their abilities aren't quite the same. They can both stretch, camouflage, harden, etc. but whereas the Venom symbiote has to maintain being a singular piece, the Carnage version can shoot projectiles of itself, that is, it can break pieces of itself away with no injury.

Venom is poison. Carnage is dead bodies.

The Carnage symbiote is an offspring of the Venom symbiote. Both of them have basically the same abilities and amplify the emotions and impulses of the person they are bonded to. Carnage is bonded to a completely deranged murderer. Venom has bonded with several people who aren't exactly nice, but they are all sensible people (usually with some sort of grudge against Spider-Man). Because of this, Carnage is more dangerous, because he actively wants to destroy everyone else in the world, and therefore doesn't hold anything back.

Carnage was once a serial killer known as Cletus Kasady, and became Carnage after merging with the offspring of the alien symbiote called Venom during a prison breakout. The symbiote amplified his psychotic nature making him even less mentally stable than he had been previously, and therefore even more dangerous.

K