We observe different phases of the Moon from Earth because of the relative positions of the Sun, Earth, and Moon, and how the Sun's light illuminates the Moon. Here's a breakdown:

* The Moon doesn't produce its own light. It reflects sunlight.

* The Moon orbits Earth. As it orbits, the angle at which sunlight hits the Moon changes from our perspective on Earth.

* We only see the illuminated portion of the Moon.

Here's how the phases work:

1. New Moon: The Moon is between the Sun and Earth, so the sunlit side of the Moon faces away from us. We see nothing.

2. Waxing Crescent: The Moon is moving away from the Sun, so a sliver of the sunlit side becomes visible.

3. First Quarter: The Moon is 90 degrees from the Sun, and we see half of the sunlit side.

4. Waxing Gibbous: More than half of the sunlit side is visible as the Moon continues to move away from the Sun.

5. Full Moon: The Moon is opposite the Sun, so the entire sunlit side is facing us.

6. Waning Gibbous: After the Full Moon, we start seeing less of the illuminated side as the Moon moves towards the Sun again.

7. Last Quarter: We see half the illuminated side again, but this time, it's the left half (from our perspective)

8. Waning Crescent: Only a sliver of the illuminated side is visible as the Moon moves closer to the Sun, leading back to the New Moon.

Think of it like a giant, illuminated ball: As the ball rotates, we only see the part of the ball that is facing us and lit up by the sun.