Okay kiddo, so imagine you have a rulebook for a game that tells you all the things you can and can't do. That rulebook is like the Bible, and lots of people believe it's really important and can help them know how to do the right thing.
Now, there are some people who believe that the Bible is the most important thing when it comes to knowing how to live a good life. They think that it's the main source of information and that everything else comes second. That's what we call "prima scriptura."
Basically, "prima scriptura" means that the Bible is the most important thing to use when you want to learn about what God wants you to do. It's like the biggest and most important piece of information that you turn to first.
But just like with the game rulebook, sometimes you may need other information too. For example, you might need to ask someone who's played the game before to explain something to you. In the same way, sometimes people might need to look at other information besides just the Bible to understand something better.
Overall, though, people who believe in "prima scriptura" think that the Bible is the most important thing they need to guide their lives.