Options exist for almost all of the tools in the toolbox.
The lasso tool works by selecting it, then dragging your mouse around an area. When you release the mouse, a connecting line is drawn between the starting and ending points. This will create a new selection, add to the larger existing selection when you hold down the Shift key, or subtract from the larger existing selection when you hold down the Alt key. The polygon lasso tool works similarly, but instead of clicking and dragging around an area, you set anchors between straight lines for a more angular selection. This is a less precise method but much quicker if you have distinct areas to encompass, and a fine curve is not needed.