It allows us to speak and keeps our food in between our teeth when we chew.
The tongue has three main functions. First, it carries on its surface the taste buds which send information to the brain about the nature of the food being eaten. It seems likely that the sensation of taste is not merely to make eating a pleasure, but also to act as a protective mechanism designed to cause the rejection of noxious (harmful) foods.
Secondly, the tongue plays an important part in the process of digestion. It enables the food to be moved about the mouth and to be placed in a position where it can most effectively be ground down by the molars. When the contents of the mouth are ready to be swallowed, the tongue forms them into a ball, or bolus, which is moved toward the pharynx at the beginning of swallowing.
Finally, the tongue is concerned in speech. By assuming different positions in the mouth it alters the shape of the air passage through which pass the sounds made by the vocal cords.