Sceneform empowers Android developers to work with ARCore without learning 3D graphics and OpenGL. It includes a high-level scene graph API, realistic physically based renderer, an Android Studio plugin for importing, viewing, and building 3D assets, and easy integration into ARCore that makes it straightforward to build AR apps. Visit this video link of Google I/O '18.
Whereas ARCore in Unity uses three key capabilities to integrate virtual content with the real world as seen through your phone's camera:
Motion tracking
Environmental understanding allows the phone to detect the size
and location of all type of surfaces: horizontal, vertical and
angled surfaces like the ground, a coffee table or walls.
Light estimation allows the phone to estimate the environment's
current lighting conditions.
ARCore is Google’s platform for building augmented reality experiences. Using different APIs, ARCore enables your phone to sense its environment, understand the world and interact with information. Some of the APIs are available across Android and iOS to enable shared AR experiences.