What is rule of thirds?
The rule of thirds is dividing your image into 2 vertical lines and 2 horizontal lines. Then you position the important elements in your scence along those lines where they meet, like it's shown in the image above.
Why do photographers use rule of thirds?
When using rule of thirds, it means that the subject isn't centered in the middle, which is how many photographers frame their shots. Instead of the main focal points being on one side, using the rule of thirds will draw the veiwers eye into the composition instead of just glancing into the centre.
My best Image is the one on the right because it shows the rule of thirds correctly, unlike the one on the left which looks a bit messy.
Here are some other images which show the rule of thirds
*This information was taken from google*