1) Eclipses occur when one celestial body blocks the light from another. Lunar eclipses happen during a full moon when the Earth casts its shadow on the moon. Solar eclipses occur during a new moon when the moon passes between the Earth and sun. 2) There are three types of lunar eclipses - total, partial, and penumbral - and three types of solar eclipses - total, partial, and annular. 3) Eclipses do not occur every month because the moon's orbit is tilted relative to the Earth's orbit around the sun. Lunar eclipses are more frequent than solar eclipses.