RULE OF THIRDS
The rule of thirds is a grid of 9 squares (3X3). The theory is to put the main point of the photo of where the lines of the squares meet to make the photo look more balanced. Photographers use this so that there isn't one space in the photo really crowded and another space with nothing to look at in and the objects in the photo is spread evenly all over the picture. Below is a photo of what the grid looks like and an example of this technique.