ARSubsystems defines an interface, and the platform-specific implementations are in the ARCore and ARKit packages. ARFoundation turns the AR data provided by ARSubsystems into Unity `GameObject`s and `MonoBehavour`s.
The `mater` branch is compatible with Unity 2019.1 and later. For 2018.4, see the [1.5-preview branch](https://github.com/Unity-Technologies/arfoundation-samples/tree/1.5-preview). ARFoundation 1.5 is functionality equivalent to 2.2. The only difference is the version of Unity on which it depends.
The `master` branch is compatible with Unity 2019.1 and later. For 2018.4, see the [1.5-preview branch](https://github.com/Unity-Technologies/arfoundation-samples/tree/1.5-preview). ARFoundation 1.5 is functionality equivalent to 2.2. The only difference is the version of Unity on which it depends.