How is a novel part fiction and part nonfiction?

Some parts can be true and some parts can be made up. A novel could be based on a true story and then the author adds in some elements of their own that did not actually happen. That is commonly done in books and also in movies. Authors often don't have all the information they need, so they have to make some things up. They may add parts to make the story more interesting or exciting than what really happened. So you get fiction and non-fiction in the same novel.