What does crack do?

because you touch it.

lols simple dont shot it up/ and or smoke it lawls

Your joints are releasing the synovial fluid and makes a cracking noise.

Well actully, when you crack your back, its not like a bone or joint cracking. Its sort-of "bubbles" in your back from spinal fluids.

Almost immediately. If you paint each nail and watch for a few seconds you can actually see it crack.