A birthmark is pretty much what it sounds like: a mark that's on your skin when you're born. Actually, though, some birthmarks show up soon after you're born.
Birthmarks come in different shapes, sizes and colors and can be anywhere on the skin. Some are so little and pale that you might not even notice them. Most people have at least a few of these.
Other birthmarks are bigger and are purple, red, or black. You might notice these more, especially if they are on someone's face. These large birthmarks might make some kids embarrassed. Other kids aren't bothered at all. Usually a big birthmark doesn't mean there's anything wrong, though. Some kids just happen to have them. Birthmarks usually don't hurt. No one really knows what causes them. Some go away on their own, and others might stick around your whole life. If you have a birthmark that bothers you, talk to your mom or dad about it. You can ask them to take you to a skin doctor (dermatologist). The skin doctor can talk to you about your birthmark and decide if it needs to be treated or if you should just leave it alone.
Next: Why people get birthmarks