You're right! We see different amounts of the Moon's surface illuminated during its phases. This is because the Moon doesn't produce its own light, it reflects sunlight. The way we see the Moon depends on the relative positions of the Sun, Earth, and Moon.

Here's a breakdown:

The Moon's Phases Explained:

1. New Moon: The Moon is between the Sun and Earth, with the sunlit side facing away from us. We can't see it.

2. Waxing Crescent: As the Moon orbits Earth, a sliver of the sunlit side becomes visible, like a tiny crescent.

3. First Quarter: Half the Moon's surface is illuminated, appearing as a half-circle.

4. Waxing Gibbous: More than half of the Moon's surface is illuminated, looking like a plump, slightly-curved shape.

5. Full Moon: The Sun, Earth, and Moon are in a line, with the sunlit side facing Earth. We see the entire illuminated surface.

6. Waning Gibbous: After the Full Moon, the illuminated portion starts to shrink, still looking like a plump, slightly-curved shape.

7. Last Quarter: Again, half the Moon's surface is illuminated, but the illuminated side is now on the opposite side of the Moon compared to the First Quarter.

8. Waning Crescent: The last sliver of the sunlit side is visible before returning to a New Moon.

In short, the different phases are caused by the changing angle of the sunlit portion of the Moon as it orbits Earth. We see more or less of the illuminated surface depending on where the Moon is in its orbit.