Rule of Thirds

"Guideline which applies to the process of composing visual images such as designs, films, paintings and photographs"

The rule of thirds has two horizontal lines and two vertical lines that split the frame into nine parts. Photographers use the intersection between the vertical lines or the horizontal lines to frame photos, shots etc. As a result, the subject of the frame is off-centre but still the main focus. Here is an example of a rule of thirds guideline being used on a photo:

As you can see, the cup is placed at an intersection and still remains the focus of the frame. Here are some photos to show the difference between a photo using the rule and one without: