Venom and Poison are both toxic substances. Still, some animals are called venomous and others are poisonous. The only difference between being called poisonous or venomous is in the way these animals deliver the harmful substance.
Venom: When animals like snakes use their sharp fangs to bite into the flesh and let the toxic substance move into the body of their prey, through the punctured skin, they are called venomous animals. To deliver venom an animal has to use tools like fangs or stingers.
Poison: Poison is something that can get inhaled, ingested or seeped into the skin directly. For example, if you accidentally touch a brightly colored poison dart frog, you will transfer the toxins it secretes from its skin, to your own skin. And then the poison will seep into your blood stream.