If you see an ant what does it do?

Answer 1

It does nothing but carries on its task.

That task, however, may be to protect the colony from invaders, and if it believes you are an invader, some species will attack. Most don't, but the aggressive "Fire Ants" in southern US states attack quickly and in large numbers. They have a sting that burns like fire and in some people can raise a blister and be painful for several days. Other people can have severe allergic responses from the venom which comes not from a bite, but from an area on their abdomen.

Another species of ants that harm you with venom are called bull ants and are mostly in Australia.