Like the penis, the clit has a foreskin that can be pulled back to expose the clitoral glans - the small piece of flesh under the foreskin that gives the clit its size and shape. See the diagram below. Touching the exposed glans with your fingers is a big no-no (unless your fingers are wet and you're sure she likes having her exposed glans touched...). The beauty of the lickjob is that the tongue is so soft and smooth and wet, it can stroke the exposed clit directly without causing irritation. During oral sex you can gently pull back the foreskin with your fingers to expose the glans, and then lick it with your tongue. Remember to use plenty of saliva for lubrication, and to stop if your female partner doesn't enjoy this.