Vic, in a nutshell, here's the drill:(posted 8892 days ago)The zone system is mainly for B&W materials. With B&W film, changing the amount of development generally changes the contrast response of the film (more development makes the contrast increase). Another way of describing this contrast increase is to say: the scene shadow areas have their density (on film) increased a little bit, the brighter scene areas have their density (on film) increased a lot.
The zone system thing is to discover the extent of these response changes with the particular film, developer and printing paper that you are using and to correlate these with your meter readings. Once you have done this, you will be in a position to control film density produced by certain specific parts of the subject which you have decided are important to you.
I imagine that what you have been reading describes the mechanics of setting up these procedures, which in essence is a simplified application of sensitometry. Hope this nutshell description helps!