There is a smooth area on the tongue. what could it be?

Variant of normal: It's not uncommon to have these bald or smooth areas on your tongue. It may be in one spot or several and may even vary from time to time. One such condition is called geographic tongue. It is completely benign and nothing to be concerned about. These areas lack the normal papillae of the tongue. It's always best to have a dentist take a look just to be sure.