An innie is an informal, playful word for a belly button that curves inward, creating a small hollow or dip in the center of your stomach. Most people have innies: their belly button looks like a tiny bowl or dimple. The opposite is an outie, where the belly button sticks out instead of going in.

Your belly button is actually a scar from where your umbilical cord was attached before you were born. After the cord is cut and heals, it can form either an innie or an outie depending on how the skin and tissue heal. Whether you have an innie or an outie is completely random and doesn't mean anything about your health.

Kids sometimes compare belly buttons and notice these differences, turning what's really just a small variation in how everyone's body formed into a point of curiosity or playground conversation. Some people with innies find that lint from their clothes collects there, which can be annoying but is totally normal.