Pubic lice, or crabs, are one of three types of lice that infect humans. They are parasites that live in the body hair, and can be transmitted during close body contact. Adult lice, though small, are visible to the naked eye. Under magnification, the pubic louse looks like a crab, which explains its nickname.
Nits are lice eggs.
Pubic lice can be transmitted by the hands to other parts of the body, or to facial hair during oral sex. Pubic lice are generally transmitted sexually, but can be transmitted by other close personal contact. Nits, or lice eggs, can survive off the body for several days. Pubic lice use claws to grasp pubic hair, and feed off blood vessels of the host human. Some people tolerate the itching well, and realize they are infected only upon visual inspection.