Contrast
Webster's defines contrast as " juxtaposition of dissimilar elements (as color, tone, or emotion) in a work of art". There are many different forms of contrast, i.e. light and dark, warm and cool, fruit and veggies. Contrast is what you get when you group a bunch of different elements together into one setting. It is the essence of variety. The image to the right shows the contrast between light and dark, warm and cold. Contrast is important in design because it helps to make the bit of work more instressing and aesthetically appealing. With out contrast every thing would look dull and boring. There would be no depth.
With out contrast this image lookes like a circle with a line behind it. Not much to it at all.
Add some basic shading and a drop shadow and what looked like a circle with a line behinde it now looks like a ball (or a cocunut according to my girlfriend's niece). My point is the shading gives depth where before there was none so now you have ssomething that looks 3d.
