system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: What are birth marks and why do we get them?

Edit: Thanks for all the replies guys loved reading them all!
gpt
**What are birthmarks?**

There are different types. Some are a bunch of blood vessels and capillaries close to the surface of the skin. These are not permanent, but are common among newborn children. This kind is usually red.

The other kind is an above average accumulation of pigment cells in the skin. These are typically brown, and are long lasting if not permanent.

**Why do we get them?**

In short, nobody really knows. There are theories about late mutations in embryo development, but the short (and real) answer is we aren't quite sure.