From Ask Yahoo!
What are dogs' whiskers for?
Whiskers are an important hunting and orientation tool for dogs as well as many other mammals. A seal's whiskers, for example, pick up vibrations in the water, allowing it to detect prey as far as 180 meters away.
The scientific term for these finely tuned sensory structures is "vibrissae." While the hairs themselves don't contain nerve endings, their base is surrounded by erectile tissue and a rich nerve supply. Like human eyelashes, they prompt the dog to close its eyes when they're brushed.
The whiskers on cats and dogs are highly sensitive to air currents and vibrations. Dogs react quickly when anything brushes against their whiskers -- see for yourself (with a friendly dog, obviously).
Many dog groomers clip their dog's whiskers for show purposes, although it can often impair a dog's ability to hunt and play.