Why is the shape of the orbits of planets elliptical?

Kepler's first law explains, that planets orbit in the shape of an ellipse with the sun being one of the focal points of the orbit. Unlike circular orbits, whose two focus points reside in the same location — the center of the circle — elliptical orbits have two focus points in different locations. In the case of the sun and the planets, the sun is not at the center of the orbit. Why? Because planets in the solar system gravitationally affect the orbits of other planets squishing what might otherwise have been a perfectly circular orbit. Instead, the sun is one focus for the planet’s gravitational pull. Usually, nothing is at the other focus point. Because the two focus points are not in the same location, the resulting orbital path is elliptical.