Introduction to Layers
Layers are a powerful feature found in Elements that I think will dramatically change the way you edit your pictures. More importantly, it will also significantly expand your creative potential.
Layers are used when we want to include more than one element in a file, such as images, text, or graphics. They're also important when we want to edit individual parts of an image without affecting the rest of the picture. Aside from retaining complete editability of all components (providing that they are on separate layers), a layered file must be saved in a special file format - typically a Photoshop or a TIFF file. Besides retaining the layers, these formats suffer no compression artifacts, are fairly universal in their use, plus they have the unique ability to contain multiple versions of the same image within the same file.