 So what is the utility of the package JSON file? That's a tough question to answer because it really does a lot. And depending on what you're using NPM for, it might be doing different things for you. But I'm going to assume right now that you are just building apps. So what's the big utility of having a package JSON in your app? Well, right now I know that if I run NPMLS, I'm going to see React and all of its dependencies. We ran NPM install to get those. And NPM install added it to our dependencies. Now, this is really important when we're building apps because maybe we're using GitHub to work with other people and push changes to this app all the time. Now, we have React, but let's assume that we didn't. Let me quickly remove everything that is in that directory, that node modules directory. We'll run NPMLS again. And whoa, it's not happy. For the first time, we're seeing actual errors. And the errors are that all of these things that we need to run our application are missing. So this is representative of someone who joins our team and clones our app for the first time. They're missing all of these dependencies. And we know that they're missing because they're in the package JSON listed right there. So now instead of that person having to specify exactly what needs to be installed, they can just type NPM install. And with the package JSON file in place, it will resolve all those dependencies. NPMLS again, and everything's perfect. This is the big role that package JSON plays when you're working with a team on an application. We'll cover how package JSON is important to library creators in another course.