What is a one-sentence summary of the following article?
This preserves a copy of the image within the Photoshop file.  If you mess up the image, you can click the layer you messed up in the Layers panel to the right.  If the Layer panel is not displayed, click Window in the menu bar and click Layers. Then click the icon that resembles a trashcan below the Layers panel to delete the layer.  Use the following steps to duplicate your layer.  Cick the background layer in the Layers panel to the right. Click Layers in the menu bar at the top. Click '"Duplicate layer.

Summary:
Duplicate the background layer.