Planetary motion refers to the movement of planets around a star, such as the Sun. This motion is governed by the force of gravity, which pulls planets toward the star while their forward motion keeps them in orbit. The paths that planets take are typically elliptical, as described by Johannes Kepler's laws of planetary motion. The speed and distance of a planet from its star affect its orbital period, or the time it takes to complete one full orbit. For example, Earth takes about 365 days to orbit the Sun, while Mercury, being closer, completes its orbit in just 88 days.