Unity features which are in development.
Unity Technologies supplies some experimental features with the standard Unity Editor installer, which you download from the Unity store. Other experimental features you need to download from the Unity Technologies GitHub and install separately, once you have installed the Unity Editor.
In-Editor experimental features
To access experimental features in Unity, go to Window > Experimental > [name of feature]
Plugin experimental features
To access Unity experimental feature plugins, download them from the Unity Technologies GitHub and install them separately to the Unity Editor.