This area documents each tool in detail. You'll get a description of each tool and its purpose. You'll see example code and configuration. And you'll see API documentation, useful for integrating the tool into your own repo.
Each tool is designed to be used on its own or in concert with others. How you use the tools depends on your needs. The CLI, for example, brings many tools together to perform common React Native developer tasks like bundling or managing dependencies. Individual tools help you solve specific problem, like making Metro work with symlinks.
If you get stuck or notice that something is missing, take a look at the Community area. You'll find talks, podcasts, recorded streaming sessions, and other materials that may help you out. You'll also find links to the developer community where you can ask questions and get help.