Eclipse-A celestial body is called under eclipse with respect to another body when, whole or a fraction of the first body is behind a 3^rd body. When this happens the body -1 is not visible partially of fully from body-2.

When this happens with respect to the Sun, the Moon & the Earth, these phenomenon are called, Solar Eclipse & Moon Eclipse w.r.t. the Sun & the Moon respectively when viewed from the Earth.

Solar eclipse- This occurs because the Moon and the Sun appear almost the same size. Solar eclipses occur, when the Moon is between Earth and the Sun.

Moon Eclipse-the Moon orbits the Earth once a month, and eclipses happen if it lines up exactly with the Earth and the Sun. Lunar eclipses occur at Full Moon, when Earth is between the Sun and the Moon.

Note:- that Eclipses do not take place every month because the orbits of the Moon and Earth are tilted at an angle. Most of the time, the line- up is not precise enough for an eclipse.