Whenever you create a new layer or duplicate a layer, you can control how the two layers will interact. You use the Blending Mode to do this. Often you will use the Normal blending mode, which basically stacks the two layers with no interaction between them. But there are 24 more in Photoshop Elements. One quick way to cycle through them and see their effect is to first select the Move Tool. Then click on Shift+ to work down the list of blending modes, and Shift- to work up.
As an experiment, stack two images, for example a portrait over a textured background. With the portrait on the top layer, and the Move Tool selected, cycle through the blending modes as described above. The figure below shows an example. In this case, the Blending Mode was Hard Mix. Remember you can vary the effect by adjusting the top layer’s Opacity.