When dealing with computer graphics, layering is the process of stacking various images, graphics, or text on top of one another. Layering in programs allows users to make alterations without changing the original image. It may also be toggled on or off, so the user may view how an image would look with or without layers.
The image to the right shows the Layers box looks like in Adobe Photoshop. As can be seen, there are four visible layers; each of which can be moved above or below other layers or hidden to effect the overall look of the final image.
Once an image containing layers is completed, it may be "flattened," combining them into a single layer. This option may be found in the "Layer" tab at the top of the screen.