Flutter provides several build modes, which determine how the app is compiled and optimized for performance and size. The different build modes are:

Debug mode : This mode is used during development and provides useful debugging features such as hot reload and logging. The app is not optimized for performance or size in this mode.

Profile mode : This mode is used to measure the performance of the app, such as CPU usage and memory usage. The app is partially optimized for performance and size in this mode.

Release mode : This mode is used to create the final version of the app that will be distributed to end-users. The app is fully optimized for performance and size in this mode, and debugging features are disabled.

JIT (Just-In-Time) mode : This mode is used during development and provides the hot reload feature, which allows developers to see the results of code changes instantly, without needing to restart the app. This mode is only available in debug and profile modes. AOT (Ahead-Of-Time) mode : This mode is used in release mode to compile the Dart code into native machine code ahead of time, which results in faster startup times and better performance.

Developers can specify the build mode when running the `flutter run` or `flutter build` commands. For example, to run the app in release mode, the command would be `flutter run --release`.

The different build modes allow developers to optimize the app's performance and size depending on the stage of development and the intended use of the app.