Kepler’s second law states that the radius vector describes equal areas in equal times. In other words, for a circular orbit the motion of the planet is uniform, but in order for an object along an elliptical orbit to sweep out the areas at a uniform rate, the object moves quickly when the radius vector is short and the object moves slowly when the radius vector is long.

More simply stated: planets sweep out equal areas in equal times and move fastest when closest to the focus of the orbit.

Therefore when a planet is at it furthest point (aphelion) it is also moving slowest. When it is at its closest point (perihelion) it is moving fastest. The velocity of the object in orbit is constantly changing depending upon the eccentricity of the orbit. The more circular the object, the more regular the speed variations. The more eccentric the orbit the greater the change in angular momentum from closest to farthest point.