The "Address" is the letter used to speak to the machine. You use X, Y & Z to address which axis is supposed to move. Of course this is followed by a position value. The location to move to.

The "Format" is how the position value should look.  An  X axis position might be displayed several different ways, depending on the machine.  The position   X 1.25   might need to be displayed as......  X01.25  or  X1.2500 or  X12500.   These 3 examples are commonly refered to as  2 digit leading,  4 digit trailing and 4 digit trailing with no decimal point.