What is the difference between a primary color and a secondary color?

Primary colors (red, blue and yellow) and the base of all colors, at least two of the three colors are present in every single color. secondary colors are the colors they make up. like red and yellow makes orange or blue and yellow makes green.

What it's saying is that colored pieces of canvases is a piece of art

It depends on what type of third separates the three notes.for example: if you have two mayor thirds is an "aumented chord"if you have two minor thirds is an "diminued chord"if you have one mayor first and then one minor is a "mayor chord"and inverted is a "minor chord"