Photoshop is a very complex tool full of a wide variety of powerful features, but perhaps no feature is more crucial to editing images than layers. If you are new to Photoshop, this great video tutorial will show you how layers work in just a few minutes.
Coming to you from Perea Photography, this excellent video tutorial will show you how to use layers in Photoshop. Layers are by far one of the most fundamental tools in Photoshop. You can think of layers as the different components and adjustments that come together to make a final image. What makes them so powerful is that by separating out these components, you can work on them one at a time non-destructively, meaning you can go back and change them later on or even remove them entirely without affecting the base image. It is a good idea to get into the habit of using layers instead of working directly on your base image as soon as possible. Beyond that, you can also use layer masks to selectively apply adjustments instead of using them across the entire image. Check out the video above for the full rundown from Perea.
And if you would like to continue on your photography journey, be sure to check out "Photography 101: How to Use Your Digital Camera and Edit Photos in Photoshop With Lee Morris!"
I once described Layers by showing someone the clip of Tony Stark in Ironman 1, the cave scene, where he lays the sketches in a pile and pushes them down to form the hidden designs of the Mark 1 suit.
Basically the sum of the layers combine into the single image using transparencies, blending modes and adjustments.