With this grid in mind you can now see where the lines intersect; which are the four important spots to place your image for maximum effect. You can also see the four "lines" that are very useful when thinking about other elements in your image and where to place them. (the red lines)

The rule states, basically, that if you place your subject along one or two of the four intersections, your image becomes more balanced and more visually appealing.  The "rule of thirds" means that you have divided your image into three sections, both horizontally and vertically, and you are going to use the intersections for your subject.

Studies have shown that when a viewer sees an image, the eyes naturally gravitate toward those intersecting lines anyway, so it is a very natural progression.

Using the Rule of Thirds can be a natural thing for some photographers, but for others, it might take some practice. For example, often, we are so used to just placing our subject directly in the middle of the image because we think that looks great. And, in some cases, it might. But, it is good to know the "rules" of composition first, and then we can break them.

If we are used to placing our subject in the middle, then we might not "feel comfortable" or we might think the image does not look "good" when we place the image where it should be. Just like anything, we need to practice and learn.

When first learning this composition rule, ask yourself these two questions.

What is my subject?

Where should I place my subject for a visually appealing image?

Once you practice enough and when you are at a point when you do not have to think about the grid-in other words, you are automatically placing your subject in one of those four intersecting lines for a visually appealing image-go ahead and break the rule.

Often, depending on what is being photographed and what else is in the image, placing your subject in a different place might make more of an impact. But, learn this first.