Layer masks are one of the most fundamental and powerful tools in Photoshop and one of the first things anyone new to the application should work on mastering. If you are new to Photoshop, this great video will show you everything you need to know about how layer masks work and how you can use them in your image editing.
Coming to you from photoshopCAFE, this great video will show you the ins and outs of layer masks in Photoshop. Fundamentally speaking, layer masks are pretty straightforward: they enable you to show or hide different areas of your image or to apply an adjustment only to a place of your choosing. This allows you to localize your work as much as you would like. The usefulness of layer masks extends far beyond simple manual selection, however. With more advanced techniques, you can create automatic layer masks that correspond to different parameters in an image, allowing you to create more complicated and intricate edits. Check out the video above for the full rundown.
And if you want to continue on your learning journey, be sure to check out "Photography 101: How to Use Your Digital Camera and Edit Photos in Photoshop With Lee Morris!"