Photography is all about light. Direction, color, hardness, it's all about light. To control what happens in your photograph you must control the light. What does that mean? Let's look at some examples of where light used well makes for some great photographs.
Assignment: What did the artists below do to get these photos? Do you think they were just lucky or was it technique? What kind of planning does it take to create photographs like these?
Look at some of the photos but save some time to explore Flickr's light clusters:Light || Shadow, Sun & Reflection || Silhouette || Backlit
This image from Barbara Fischer's Flickr stream uses backlight to bring out color and texture of the leaf.
Backlight acts to frame the image with light and creates sharp definitions of interest within the photograph. Take a look at the backlight pool on flickr for more examples.