Layers are similar to stacking sheets of acetate, like overhead projector sheets.
See the basic layers description in my previous article on Photoshop layers . Layer are not exactly a subject to make your heart beat fast, but they are essential to working efficiently with almost any graphic program, especially raster programs. Before layers were introduced, adding new objects to a document was very high on the stress meter. Now we not only have the ability to keep raster items separate, we also have powerful layer-based effects in our toolbox. Understanding how layers work not only gives us the power to organize, but also to add artistic appeal to our images.