Kepler stated three laws of planetary motion.
First law states that the pathway of a planet is an ellipse with the Sun at one of the foci.
Second law states that an imaginary line joining the Sun and a planet sweeps out equal areas during equal lengths of time.
Third law states that the square of the period of the orbit of a planet is directly proportional to the cube of the length of the distance from the Sun.
Therefore, the answer is that Kepler's second law of planetary motion states that planets cover the same area during equal time periods.