The Walter Scott Prize is a really fancy award given to really good books that are based on or inspired by history. It's like a big gold star for authors who write about cool things that happened a long time ago. Think of it like your teacher giving you a special sticker for doing really well on a project that you worked really hard on, except the sticker is a big prize and the project is a big, thick book.
It's named after a man named Sir Walter Scott who was a really famous writer a long time ago. He wrote books about Scottish history and other cool stuff like that. So, this prize is kind of like a way for people to remember him and all the awesome things he did.
When an author writes a book that they think would be good for the Walter Scott Prize, they send it in to be judged by some really smart people who know a lot about history and books. These judges read all the books and decide which one is the best. So, it's kind of like a contest, but instead of playing games you write a book and people judge it to see how good it is.
Then, once they decide which book is the best, the author gets to win the Walter Scott Prize and everyone says how great their book is. It's like getting a really special trophy that you can keep forever and show to all your friends and family.