The term 'Type of Navel' refers to the two different shapes of the human belly button. An 'innie' is a navel that is indented, while an 'outie' is a navel that protrudes outward. Innies are the most common type of navel, and are caused by the umbilical cord being pulled inward during the healing process after birth. Outies are less common, and are caused by the umbilical cord not healing properly.