What is the rule of thirds in photography?

The Rule of Thirds

When observing the scenery through the viewfinder, imagine dividing the picture into three equal parts. Where the lines intersect is where the center of interest and other secondary features are arranged. Of course, this rule can be applied flexibly. The center of interest does not necessarily have to be exactly at the intersection, but it must be roughly in that area. Those intersections on the right end of the picture are usually considered to be the strongest; of course, the left third is sometimes used to arrange the center of interest, depending on how the picture is balanced. The rule of thirds applies to both horizontal and vertical formats. Arrange the subject and companion according to the rule of thirds, and the photo will appear compact.

Excerpted from Pacific Computer Network