Great to hear that this helped you to understand the concept, Deborah. It is difficult to pull the three characteristics but once you are able to do that and see the difference it is amazing how much more sense everything else about color becomes.
Beginning at the upper right red square and working both down and across you reduce the chroma in each square. This is true because any time you mix any other color with a pure hue you reduce the chroma.
As you noticed the value also changes.
Starting at the top and working down the value of the squares in each column are darker than the one directly above.
Starting at the right and working left the value of the squares in each row are lighter than the one directly to its right.
The chart just shows varying degrees of change in chroma and value as you get further from the original hue.