A booger is dried mucus from inside your nose. Your nose produces mucus (that slimy, wet stuff) to trap dust, dirt, germs, and other particles before they can get into your lungs. When that mucus dries out, it becomes crusty and turns into what we call a booger.

Everyone gets boogers because everyone's nose is constantly working to filter the air we breathe. You might notice more boogers when the air is dry, when you've been in a dusty place, or when you're getting over a cold. Some people pick their nose to remove boogers, though most adults will tell you this isn't polite to do in public.

The word booger is casual and slightly silly-sounding, which is why kids often find it funny. In more formal or medical settings, people might say “nasal debris” or “dried mucus,” but booger is the everyday word most people use. While boogers might seem gross, they're actually evidence that your nose is doing its job of keeping unwanted particles out of your body.