I don't really know what you want to know - I have looked at the Galil 1832 card and as far as I can see this card fits inside the P.C. and then drives your motor amp/driver cards. It quite clearly generates much of the signal pattern for the motors.
Mach 3 on the P.C. does away with the Galil 1832 card as far as I can see. It generates the control signals.It provides step and direction control for each axis (which connect directly to the axis motor driver cards, a step/direc or a PWM signal for spindle control, and input/ouput lines for limit switches, coolant etc.
The output from the computer is via the 25 pin printer port (LPT1), or the latest card is a USB decoder, which connects to your computers USB port and decodes the signals. (This card generates the pulses for the various motors, taking away some of the work from the host PC.)
Mach 3 is a full featured CNC program. You can download a version to test and inspect. That is also full featured, but only runs 500 lines of code - which is you are doing pictures of a ship on a choppy sea, will soon be used up.
What else do you want to know - what is you mill, and how is it run - servo's, steppers - limit switches, spindle control ??