The orbit of every planet is an ellipse with the Sun at one of the two foci.

This means:

* Planets do not move in perfect circles around the Sun. Their orbits are slightly elliptical, meaning they are oval-shaped.

* The Sun is not at the center of the ellipse, but at one of the two focal points.

This law revolutionized our understanding of planetary motion, replacing the previous belief that planets moved in perfect circles. It paved the way for a more accurate description of the solar system.