The rule of thirds is a visual principle that offers a guideline in the composition of designs and photographs. It states that a design/composition can be divided into nine equal parts that are separated by two horizontal and two vertical lines.
The most important parts of this grid are the four intersection whereby the most important parts of the image should be placed.
In the example that is illustrated below, you can see that the lorry occupies the two intersection on the right and the curvature of the road the bottom right.
The result of which is a naturally balanced image.
By using the 'Rule of Thirds' you can highlight the most important information/functions of your design/photograph allowing your user to easily scan and interpret your work. The practical application of this guideline will help designers/photographers/artists to deliver natural composition or a message that consistently works visually.