What Is the Difference Between the Terms Color Intensity and Color Saturation?
When you take an RGB Image matrix and convert the color into HSV Color Model the color is represented on Cylinder.
Now, the intensity (Lightness / Value) is the height on this Cylinder which is going from black to white and basically sets the Gray Color of the neutral color (One which blends RGB in the same intensity).  

Saturation is the Radius and intuitively is how far the color is from being neutral (Pure Gray).
Namely, how dominant is one color component versus the others.