An eclipse occurs when one celestial body passes between the sun and another, blocking sunlight or moonlight. There are two main types of eclipses - lunar eclipses, where the moon passes into Earth's shadow, and solar eclipses, where the moon passes between Earth and the sun. During a lunar eclipse, the moon turns red as it is illuminated only by sunlight passing through Earth's atmosphere. A solar eclipse can be partial or total, where the moon completely blocks the sun's light over a small area. Total solar eclipses are rare as the moon's shadow is small and its orbit is tilted relative to Earth's.