To use a monitor calibration unit, the monitor needs to be reset to the factory default settings,
i.e. no brightness / contrast or other adjustments. The monitor cannot be too old, i.e. 10 years
with the brightness turned up to the highest value for the last 5, or you will not be able to adjust
the brightness / contrast to within the specs the calibration unit needs.
The software leads you through the process and guides you while setting these controls. Then the
calibrator is placed on the screen where the software projects a series of known colours (i.e. it knows
what the RGB values of these colours are) and measures them. When the process is finished it compares
what it has read to what it was supposed to read an makes a adjustment file which is controlled by the
software on the computer from startup each time. Whenever a colour displayed on screen it passes
through that file (kind of like a filter) and is adjusted accordingly so that it matches as closely as possible
the colour it was actually supposed to be.