Hello, little one! So you know how there's a big book called the Bible that talks all about God and Jesus and stuff? Well, some people wrote other books around the same time that talk about those same things but weren't included in the Bible. These books are called "non-canonical" because they aren't part of the official set of books that was chosen to be in the Bible.
Now, even though these books aren't officially in the Bible, people still talk about them because they can give more information about what life was like back then and what people were thinking and believing. Some people think these non-canonical books are really important, and some people don't think they're important at all. But either way, they can help us understand the Bible better!