Venom is a kind of poison used by animals. It is made in an animal's body. It is injected into the body of another animal by a bite or sting. Animals that use venom include some kinds of insects, fish, reptiles, and even mammals.
Some animals use venom to kill another animal that they are going to eat. One animal that does that is the rattlesnake. Some animals use venom to protect themselves. Some animals that do that are bees and ants. Some animals use venom for both of these things.