The selection tools allow you to select areas from a layer or even an entire image. As you might imagine, creating selections, filling selections or making selections transparent gives a lot of possibilities for a multi-layer graphic.

CHECK YOUR UNDERSTANDING:
Try the various selection tools yourself. Try different settings (particularly THRESHOLD on the Color Selection Tool). See if you can use the Paint Can (fill) tool or the Gradient Tool to fill in your selections! Download the included .ZIP file for examples.