Okay kiddo, so let's talk about surnames. A surname is like a special name that tells us which family someone belongs to. It's like a family name!
Now, Rossant is a surname. It belongs to a family called the Rossant family. Surnames can be passed down from parents to their children. So if a person's dad is named Rossant, then their last name would also be Rossant too!
People might use their surname to help them find out more about their family history. They might even try to trace back their family tree for many generations!
But remember, just because someone has a certain surname does not mean they are exactly like other people with the same last name. Everyone is unique, even if they share the same surname!