As the Earth goes around the Sun, it will appear that Earth is stationary and Sun is going around it. One can observe the same in real life as well. This apparent path followed by the Sun is called Ecliptic. The plane consisting Ecliptic is called as Ecliptic plane which is same as the orbital plane of Earth.
All the planets of the Solar system are also going around the Sun. Their orbital plane has negligible tilt with respect to Ecliptic plane. Due to this the planets will always appear near to the Ecliptic as they move on the celestial sphere.
Joel has a steeper slope on the graph. The steeper a slope is, the faster speed will be. Therefore, Joel's slope is steeper which increases overall speed.
