This is a Southern Black Widow spider. All spiders are venomous, which means that when they bite, they can inject a toxin. The Black Widow's venom is very toxic to people.

They are not poisonous. Things that are poisonous are toxic when eaten. Black Widow spiders are eaten by birds, wasps, and many other creatures. Some kinds of spiders are eaten by people, and are considered to be quite tasty, if cooked properly.