Marquee: this tool allows you to select an area of an image within a particular shape. The default is rectangle, but there is also an ellipse selection as well as a single row and single column marquee.
Lasso: this tool allows you to select irregular areas of an image. There is also the freehand lasso tool and the magnetic lasso tool (which will find the edge of an element within the image you are trying to select).
Magic Wand: the magic wand tool is another tool that you can use to select an area on the screen. It is used when you want to select an area that contains the same color throughout.