Rule of thirds

The rule of thirds is a "rule of thumb" or guideline which applies to the process of composing visual images such as designs, films, paintings, and photographs. 

The guideline proposes that an image should be imagined as divided into nine equal parts by two equally-spaced horizontal lines and two equally-spaced vertical lines, and that important compositional elements should be placed along these lines or their intersections. The rule of thirds is applied by aligning a subject with the guide lines and their intersection points, placing the horizon on the top or bottom line, or allowing linear features in the image to flow from section to section. The main reason for observing the rule of thirds is to discourage placement of the subject at the centre, or prevent a horizon from appearing to divide the picture in half. 

In the rule of thirds, photos are divided into thirds with two imaginary lines vertically and two lines horizontally making three columns, three rows, and nine sections in the images. Important compositional elements and leading lines are placed on or near the imaginary lines and where the lines intersect.