All apps in Expo and React Native are made out of components. These components are small reusable pieces of your app, all working together. Each of these components usually has a single responsibility. It can vary from rendering styled text, or rendering other pre-styled components to create a form.

Just like normal React, your app all descends from a single component. This component renders all other components in your app, from screens to simple text. Instead of rendering this component to DOM, Expo and React Native renders it for you using a concept called the entry point.