What is the difference between device space and world space? (HTC Vive)


i’m currently working with the HTC Vive in Unreal and have a problem with the:
GetTrackedDevicePositionandOrientation function from the SteamVr Blueprint Entry.

It says: "Gets the orientation and position (in device space) of the device with the specified ID ".
So i tried to look up what device space is in this context and found nothing.

I thougth it is just the world space seen from position (0,0,0); to confirm this i did some measurements
and came up with different results for this function, compared to a MotionController.getWorldLocation() function.

Is there a way to transform device space to world space?