The Eraser Tools
Before computers, graphic design studios used a range of analog drawing tools such as pens, pencils, brushes, and charcoals. They also used a range of erasers to remove mess, mistakes, and drawing errors. Photoshop Elements also has a range of eraser tools, the most useful being the Eraser Tool. Use this to remove excess pixels when blending different pixel layers together, for example. The Eraser Brush works with all brush tips, and if used on the Background Layer (the bottom one in the layer stack), it will always erase to the background color (which will be white by default). If you are erasing on a duplicated layer, it will reveal the pixels on the layer immediately beneath it.
The Eraser Tool has three brush modes: Block, Brush, and Pencil—although I think the Brush setting is the best for most retouching tasks, as it's the softest and most controllable. The speed of the erasing process is controlled by the Opacity slider in the Options Panel...