Photoshop Elements :: Using Layers To Edit Photos On 12?

I am still having a difficult time understanding how to use layers to edit photos in photoshop elements 12. All of the tutorials I have viewed about this have one common theme: the best way to edit photos in photoshop is to create multiple "layers" of the original background image so that different types of edits can be made to each layer, and not the original. This way the edits made to each layer can be compared to the original to make sure everything looks the way it should. Once all the edits have been made, then each layer is merged into one final touched up image, correct? Here is what is driving me mad. I have been lead to believe that when I edit a layer of an image, that any edits I make are only supposed to show up in the active layer and not in the original or any of the other layers I create. Is this true? If so, how can I set up my editor so that the edits I am making are only showing up in the layer I am actually working on? It seems to me that if the edits I make are going to show up in every layer, along with the original, then there is no need to use layers at all for editing photos.