ARCore

ARCore is a platform for building augmented reality apps for Android devices. ARCore uses three key technologies to integrate virtual content with the world through the camera. It uses motion tracking, environmental understanding, and light estimation. ARCore works by tracking the position of the device as it moves and builds its own understanding of the real world. It is able to identify interesting points and readings from the phone's sensors and has the ability to determine both the position and the orientation of the phone as it moves. ARCore only has a few supported devices at the present time, which are as follows:

If you don't own one of these devices, you are stuck using the Android Emulator for testing purposes. This is a very obvious downside, since not everyone owns one of these specific phones; additionally, the Android Emulator is an experimental piece of software and is subject to change often. The upside is that ARCore works with Unity3D and Unreal Engine as well as native to Android devices using the Java programming language.