Center-column - Top and Bottom
Center Column
The center column of the front page typically contains page content published to the front page from other areas and pages. It is divided into a center top and center bottom so that multiple blocks and content can be published.
Center column top
Center column bottom
Additional Notes
1, 2, and 3 Column Pages
When working with columns and blocks it can be specified that certain blocks appear on only certain pages, or all pages. From what I have seen this is controlled by the selected theme. So it is possible to select a 3-column theme and have only one or two columns on some pages, while others have the full three.
Fluid vs Fixed width
The fluid vs fixed width also adds another element to the mix. If you specify fluid and use only one or two columns on a page, text and images will span the entire width of unused space on the page. I am still researching and adding Full HTML input formats for authorized users to use when creating content.