Building your project with Expo allows you to make most changes in JavaScript. This helps iterate quickly and safely and allows your team to achieve web-like iteration speeds by dividing your application into:
A native runtime: A native binary that is built with Xcode or Android Studio. Expo Go is an example of a native runtime for developing React Native apps.
An update: A bundle of your application's JavaScript code and assets (images, video, fonts, and so on). An update can be served from your local computer with Expo CLI, embedded in the binary by EAS Build, or hosted on a publicly available server.
When your project requires custom native code, a config plugin, a custom runtime version, or a reduced bundle size of the app, you can transition from using Expo Go to develop to a development build.
A development build of your app is a Debug build that contains the expo-dev-client package. Like a production build is for the general public, and a preview build lets your team test your next release, a development build lets developers iterate as quickly as possible. It comes with extensible development tools to develop and test your project.
You can think of a development build as your own version of the Expo Go client.
The expo-dev-client package is used to create a development build. It is a library designed to support any workflow, release process, or set of dependencies in the Expo/React Native ecosystem. Whatever your project needs, either now or in the future, you'll be able to create a development build for it and get the productivity and quality of life improvements of JavaScript-driven development.