Kepler’s first law of planetary motion describes the shape of the planets’ orbits around the Sun. It is also called the law of ellipses. It states that:

The planets move in elliptical orbits with the Sun at one focus.

Ellipses are stretched circumferences. The orbits of the planets in the Solar System are ellipses, but their eccentricity is so small that they look like circumferences. The Sun is at a focus of the elliptical orbits, displaced from their center.

Figure: An image of the orbits of the inner planets of the Solar System to scale. For comparison, an additional orbit of high eccentricity is shown.