Layers are used in editing when images are going to be processed on a later stage. With layers, objects or products, the background or other elements (e.g. shadows/reflections) can be positioned on various levels. Layers can only be used in conjunction with a PSD or Tiff file. Different levels contain various characteristics. For example, the edited product can be on one level, the background on another level, and the path, shading or retouching on another level, etc.