I have started in on lesson five Photoshop videos on Lynda.com which is titled Introducing Layers.
You first have to unlock the flat background (because flat photos cannot be layers) so you can create an independent moveable layer.
You double click anywhere on the background box, in which a new layer box. So you can change the name of the layer.
So then you can move the independent movable layer around the screen in which the checkered background shows.