How to use Vuforia unity get Hololens camera pose

Hi, everyone

I follow the official building step and success to build AR function on the Hololens.

the link https://library.vuforia.com/articles/Training/Developing-Vuforia-Apps-for-HoloLens

Here 's the problem,

I want to know the relation between Hololens and marker.

When I read  main camera and ImageTarget value.

Both of them are not fixed value. 

Is the camera is moving while catching the marker image?

As setting step stage, we set hololens to be Central Anchor Point.

Is the world coordinate is equal to hololens coordinate? 

here my code :

A=Camera.main.transform.position //is not fixed value

imagetargetcoordinate = GameObject.Find("ImageTarget");

imagetargetcoordinate.transform.position//is not fixed value

Thanks