Okay, kiddo, so a carter is someone who used to drive a cart. What's a cart, you ask? It's like a big wooden wagon that people used a long time ago to carry things around.
Nowadays, the name "Carter" is used as a last name for lots of people. This is because, back in the day, when someone was known for driving a cart, people might call them something like "John the Carter." Over time, the "the" part got dropped, and "Carter" became a last name on its own.
So now, there are lots of people with the last name Carter, and it all goes back to those folks who used to drive carts centuries ago. Pretty cool, right?