FORM (Drawing):
The outlines of an object and the sense of it's bulk. The third dimension on a flat surface.
TONE:
The degree of lightness and darkness of what you want to paint. Changes of value and value relationships.
COLOR:
Hue
Form, tone and color are not the only things you have to master to complete your education. But they are the big three Everything hinges on getting them right.
I'll go into detail on each in later posts.