I don't have any screenshots at the moment, but it works very similarly to the dozer systems, just more sensors on the boom/stick/bucket linkage. Typically I leave it on plan view for most work. If you were working strictly on slopes, x-section or profile might work better. The system comes with lightbars also, but a quick glance at the screen once and a while as the bucket comes back is all that is needed. Staring at the screen, IMO, would be unsafe and may point to someone who can't hold a grade without GPS.
Horizontal offsets allow you to select a line on the screen, may it be a contour, pad outline, pipe run, etc. (alignment) and adjust the grade. For example, if you want to grade a road to 3' behind curb, you would align with the curb line and offset horizontally 3 feet. For Vertical offsets, if your FG is a 488 foot elevation, but there needs to be 6 inches of top soil, a -0.5' vertical offset (ie 487.5 feet) would let you grade out the area, and leave it low enough for topsoil.
Northing, Easting, and elevation are your exact coordinates in a 3-d (X,Y,Z) plan. Another way to put it latitude, longitude, and height (above sea level) Hope that helps, I'll look into getting screen shots later.