A cough, also known as tussis, is a voluntary or involuntary act that clears the throat and breathing passage of foreign particles, microbes, irritants, fluids, and mucus; it is a rapid expulsion of air from the lungs. Coughing can be done deliberately or as part of a reflex. Although coughing can be a sign of a serious illness, more often, it will clear up on its own without the need for medical attention.

Source: Medical News Today