An adjustment layer is an independent layer of color adjustment that you can edit any time you like. Plus, it affects all layers below it, consumes very little space in memory, and affords the opportunity for selective edits.
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.