It is important to keep in mind
that in all cases, pornography is restricted to consenting adults, so photographing or videotaping people under 18 in sexual situations, (i.e. child or kiddie porn) is illegal in the United States. It is also illegal for anyone under 18 to purchase pornography. Still, some teens, possibly you yourself, may encounter pornography long before becoming an adult.
How can I learn more?
Check out Feminists for Free Expression and The Anti-pornography Movement.