The mouth is an organ in humans and in many animals. Birds also have a mouth, but it is called a beak, which they have instead of lips. In mammals, one speaks of the mouth or the snout. What is special about the human mouth is that its lips are red.
The mouth is an opening in the head through which we eat. Food is chewed and moistened in the mouth. The saliva prepares it for digestion. Food and drink then pass through the oesophagus into the stomach. The tongue is a large muscle in the mouth.
The tongue turns the food as it is chewed and continually pushes it between the teeth. They can be used to break down the food. The tongue also helps you to swallow. The taste buds are located on the tongue and are used to taste.
You can also breathe through the mouth, just like through the nose. Breathing through the nose has the advantage of making the air moist. However, the nose can become blocked, for example due to a cold, in which case breathing through the mouth is the only option left. Many animals cool their bodies with their tongues because they cannot sweat: A lot of saliva evaporates on the tongue when breathing. This cools the tongue.
In addition, the mouth is there to make sounds. We already know this from animals that roar or hiss. This is how they threaten other animals. Of course, humans also need their mouths to speak or sing. However, the sounds do not originate in the mouth, they are only changed there. The sounds originate in the throat. The vocal cords are located there in the larynx.