Coordinate Readouts

I'm new to Librecad and haven't been able to find an explanation of the coordinate read outs down on
the lower left corner of the screen.  There are two different coordinates that change dynamically as I move
the cursor around the screen.  The left one seems to make the most sense to me as it seems to be accurately telling me where I am in the 2D space.  Can someone explain to me what the coordinate on the right is telling me?  

That's the cursor position relative to "relative zero", the last used point, indicated by the small red circle with a cross in it.

Had the same issue with explanation of coordinate numbers.  

The numbers on the left, what are those numbers relative to?

Also, I am unable to find what size of a square, rectangle, line etc., I am drawing on the screen.  Also when selecting an object I am unable to find what the size of the object is.

Can I tab into the size to give exact dimensions as I am drawing?

I have looked thru the manual and did not find anything, assuming that these questions are so basic that they were not covered.

Thanks
TN

Which manual?
https://librecad.readthedocs.io/en/latest/getstart/configure.html?highlight=status%20bar#status-bar
https://librecad.readthedocs.io/en/latest/ref/fundamentals.html?highlight=coordinate#the-coordinate-system

Use Info tools to measure entities or add dimensions.
https://librecad.readthedocs.io/en/latest/ref/tools.html?highlight=info#info
https://librecad.readthedocs.io/en/latest/ref/tools.html?highlight=info#dimension

Relative coordinates show length/angle of entities during drawing.
But for exact length drawing, it is recommend to use the command line.
Then you must not necessarily measure entities you have drawn.

Armin