The Three Column Layout offers left navigation, a Main Content area in the middle and a Right Sidebar. It used to be the recommended page layout, however, we have adjusted our layout practices to adhere to current standards and are phasing it out. The new preferred layout is the Two Column Layout.
Here is an example of a Three Column Layout in edit mode:
Here is an example of a Three Column Layout from the old College of Liberal Arts and Social Sciences website:
Changing the layout of a page is easy -- here's how: Changing a Page Layout.