Yes, you can only see a portion of the moon at any given time. This is because the moon orbits the Earth, and the angle at which the sun's light hits the moon changes as it orbits.

Here's a breakdown:

* Phases of the Moon: The different shapes of the moon we see are called phases. These are caused by the changing angles of sunlight reflecting off the moon's surface as it orbits Earth.

* Lunar Cycle: The moon goes through a complete cycle of phases approximately every 29.5 days.

* New Moon: During the new moon, the moon is between the Earth and the sun. We can't see it because the sunlit side is facing away from us.

* Waxing Crescent: As the moon moves, a small sliver of the sunlit side becomes visible.

* First Quarter: We see half of the moon illuminated.

* Waxing Gibbous: More than half of the moon is illuminated.

* Full Moon: The entire sunlit side of the moon faces Earth, and we see it fully illuminated.

* Waning Gibbous: We start to see less of the illuminated side.

* Last Quarter: Again, we see half of the moon illuminated.

* Waning Crescent: We see a small sliver of the illuminated side before it disappears completely.

So, why can't we see the whole moon all the time? The moon itself doesn't change shape, it just reflects sunlight. We only see the portion of the moon that is illuminated by the sun and facing Earth at that particular moment.