The Rule of Thirds, ROT, is a skill taught to photographers at the very beginning of their education.
It is about composition. It's the difference between a well thought of, good looking photo, versus a quick snapshot with uncle Johns feet chopped off at the bottom.
Take the photos below for example. The one on the left is...well, awkward. For one thing I chopped off his feet at a strange point! But when you look at the photo on the right, just shifting batman to the left a little bit, he's now lined up with the left vertical line, The photo becomes more appealing, doesn't it?
So you want your pictures to look better? Enter, Composition; the Rule of Thirds.
The point of ROT is being aware of the placement of your subject. Imagine this grid (above) when you put your camera to your eye. Place your main subject on one of the cross points (red circle- below) or along one of the lines.
Doing this can create a more interesting and compelling photo. Emphasis on can, because breaking this "rule" doesn't necessarily mean you have a terrible photo. Art is always up to interpretation. ROT is a guideline. It's a starting point to help your photos begin to take off.
Imagine using this grid the next time you pick up your camera (or i-phone even!). With practice, you'll find yourself getting away from what everyone else's pictures look like, and begin shifting to a unique piece of art.
And don't rely on that handy crop tool in post processing. Challenge yourself- get it right in camera. You've got this.