Rap--it wasn't sticking its tongue out at you, it was smelling you.

They do not use the same type of olfactory organs that humans do, we smell by using our noses, snakes use something completely different to detect odor particles in the air. Snakes use highly specialized organs in the roof of their mouths to collect particles from the air. The Jacobson's Organ is named after the individual who discovered this unique organ. A snakes' tongue will move in and out rapidly to pick up particles floating in the air and deposit them on the roof of the mouth where the organ is located.