ARCore provides two plugins for Unreal development.
Google ARCore: includes both Google's implementation of the Unified Unreal AR Framework as well as ARCore APIs that are specific to Android.
For documentation on the Unified Unreal AR Framework, which lets you build AR apps for both Apple and Google handheld platforms, see:
This section contains reference docs for ARCore APIs that are specific to Android and are not part of the Unified Unreal AR Framework.
Google ARCore Services: contains ARCore cross-platform features, such as cloud anchors. Using this plugin along with the Unified Unreal AR Framework will let you build AR apps with persistent and sharing capability using a single unified API that can run on both ARCore and ARKit platforms.
For step-by-step instructions and overviews to get started with ARCore for Unreal, see the Unreal ARCore quickstart.