According to the definition of wikipedia, Layers are used in digital image editing to separate elements of an image. A layer can be compared to a transparency on which photo effects or images are applied and placed over or under an image. Today they are an integral feature of image editors.After you evaluate some software like Photoshop, 5DFly Photo Design or others, you may get more familiar with the conception.
The standard kind of layer is called simply "Layer" in most programs. It contains just a picture which can be superimposed on another one. The picture can cover the same area as the resulting picture, just a part of it, or, in some cases, a bigger part than the final picture.
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