Q:

How to use POSE in ARCore?

The ARCore documentation defines Pose as :

Pose represents an immutable rigid transformation from one coordinate space to another. As provided from all ARCore APIs, Poses always describe the transformation from the object's local coordinate space to the world coordinate space. The transformation is defined using a quaternion rotation about the origin followed by a translation.

What is object's local coordinate space and world coordinate space?

A:

You can think of the objects local co-ordinate space as the x, y and z axis for just the object itself and the world co-ordinate space as the x, y, and z axis of the entire world that you are viewing in your preview.
In other words the local space is as if the object just exists by itself. You can rotate, tilt, zoom etc the object in this space in the usual way.
When you want to show your object in the real world every point on the object in the local space, which will have an x, y, z, co-ordinate in that local space, needs to map to an x,y,z in the world space.

