What is the epiglottis?

See below: It is a small piece of tissue just behind the base of the tongue in the throat. It's basically a lid with a hinge. Its purpose is to covert the top of the trachea (windpipe) when you swallow so that the contents in your mouth go down your esophagus and not the trachea into your lungs. That would cause choking and risk infection like pneumonia or other damage to the lungs.