The 'rule of thirds'

The 'rule of thirds' is a photography technique whereby  an image down into thirds (horizontally and vertically) so that you have 9 sections. As the example below shows:

 The ‘rule of thirds’ now highlights four important parts of the image that should be used for placing points of interest in the image. The idea is that if points of interest are placed in the intersections along the lines, the photo becomes more balanced and will enable the viewer of the image to interact with it more easily.