The term 'belly button type' refers to the shape of a person's navel. An 'outie' is a protruding navel, while an 'innie' is an indented navel. Outies are created when the umbilical cord does not heal properly, leaving a small lump of scar tissue on the surface of the skin. Innies are the most common type of navel and are created when the umbilical cord heals completely, leaving no scar tissue.