Much can be said of masking: Masking is the art of using the image to select itself. Masking lets you apply the entire weight of Photoshop to the task of editing a selection. And masking, thy name is alpha channel.
America likes its lists, and here’s another one. Imaging expert and award-winning author Deke McClelland presents his list of the top 40 features in Photoshop—beginning with #40 and working his way up to #1—one weekly video at a time. Some are tools, others are commands, still others are conceptual. All are invaluable. Learn these 40 features and you’ll know Photoshop.