Crabs or Pubic Lice is basically lice on your pubic hair, simple as that.
And no, shaving off your pubic hair does not work to get rid of it. Try not to scratch though, all that does is spread the lice!
You can get crabs from towels, beddings or clothing that carries lice. Some symptoms include itchiness and visible live bugs in hairs.
If you get crabs, you must go to your doctor before you spread it. You doctor usually gives you creams and shampoos that are specialized for crabs.