As the Moon orbits Earth, the angle at which sunlight hits the Moon's surface changes, causing different portions of the Moon to be illuminated. This results in the Moon appearing to go through different phases as seen from Earth.

The eight primary phases of the Moon are:

1. New Moon: During the New Moon phase, the Moon is between Earth and the Sun. The side of the Moon facing Earth is not illuminated by sunlight, making it appear as a dark circle.

2. Waxing Crescent: As the Moon moves in its orbit, a small crescent-shaped portion of the Moon becomes visible from Earth. This is the Waxing Crescent phase.

3. First Quarter (Waxing Gibbous): When the Moon is at a right angle between the Sun and Earth, half of the Moon's illuminated side is visible from Earth. This is known as the First Quarter or Waxing Gibbous phase.

4. Full Moon: When the Moon is opposite the Sun in the sky, its entire face is illuminated and visible from Earth. This is the Full Moon phase.

5. Waning Gibbous: As the Moon continues to move in its orbit, the illuminated portion gradually decreases. This is the Waning Gibbous phase.

6. Third Quarter (Waning Crescent): When the Moon reaches another right angle between the Sun and Earth, only half of the Moon's illuminated side is visible from Earth. This is known as the Third Quarter or Waning Crescent phase.

7. Waning Crescent: The illuminated portion of the Moon further decreases, forming a thin crescent shape. This is the Waning Crescent phase.

8. New Moon: The Moon returns to the position where it is between Earth and the Sun, and the cycle repeats.

The phases of the Moon occur in a regular pattern that repeats approximately every 29.5 days, which is known as the lunar cycle.