Click on 'Tools -> Pallettes -> Selection Info' and the Selection Info Pallette will be shown.
This is a window that gives details for the currently selected object.
If you then click on any object in the design space...for example a line...you will see the detailed information for that object.
In the case of a line, it will show 'Metrics', such as 'Start Point', 'End Point', 'Length' and 'Angle'
If you set the WorkPlane and the WorkPlane Origin before adding or modifying new objects, the values shown in 'Metrics' will be consistent across all objects which were drawn with the same WorkPlane Origin (implying the same WorkPlane).
If you do not set the WorkPlane and WorkPlane Origin, the values seen in 'Metrics' in the Selection Info Pallette will not be consistent across all objects. This is true because some objects were not drawn on the same WorkPlane as other objects.
It is brutally crucial that you keep track of the WorkPlane when drawing multiple objects, if you want to be able to change object locations and see their relative locations in the Selection Info Pallette. All Objects in 2D space must be on the exact same WorkPlane to be able to use the Inspector Bar to change Scale X,Y,Z, Size X,Y,Z, Position X,Y,Z, Delta X,Y,Z, Rotate X,Y,Z and Delta Rotate X,Y,Z and see sensible values in the Selection Info Pallete ('Metrics').
Otherwise, it will get very confusing when looking at the Selection Info from one object to another. Your point of reference will be moving, making it impossible to draw anything of any complexity without taking forever to do it.
While I'm working on multiple objects in one design I create both a reference facet (I use an extruded box) and a set of crossing lines on that facet (the crossing lines don't have to be inside the box...they can be anywhere that's convenient), which I use to get back to an exact WorkPlane. I use 'By Facet' followed by 'WorkPlane Origin' to restore the UCS to the exact WorkPlane I want to use for the design. If I need to use more than one WorkPlane I create a new facet and crossing line pair.
In some of my designs I have over 20 Facet/crossing line pairs. I locate each of them on their own custom SCONSTRUCTION layer (SCON1, SCON2, etc.) so I can temporarily hide them.
Other people may have other ways of doing this...this is just what works for me.