In the broadest possible sense, the state of an app is everything that exists in memory when the app is running. This includes the app’s assets, all the variables that the Flutter framework keeps about the UI, animation state, textures, fonts, and so on. While this broadest possible definition of state is valid, it’s not very useful for the architecture of an app.
When we're discussing managing state, it's really a discussion about the best practices in the design of your code to change the state of your application. There are many libraries that provide techniques to help us manage state. Many of which were around before Flutter. As this guide is developed, we intend to talk about those different approaches.