The Selection Tools
A selection is a feature that's used in Elements to isolate part or parts of an image in order to precisely limit the area affected by your editing. A typical example would be to select a pale-blue sky in order to darken it without touching the rest of the picture.
Photoshop Elements comes with a range of excellent selection tools, each designed to make the often complicated process of selecting objects a little easier. What many who use this program don't know is that each of the selection tools can be used in isolation or combined, simply by changing tools and continuing to click in the image. Holding the Shift key while clicking means that, as you click in the image, every click adds to the base selection. Holding the Alt/Opt keys while you click does the opposite, removing them from the base selection.
You'll note that Elements' selection tools occupy their own space, called Select, on the Tool Bar. Adobe includes the very useful Move tool in this...