Here's why:

* Tidal Locking: The moon is tidally locked to Earth. This means that the same side of the moon always faces us.

* Lunar Phases: The phases of the moon (new moon, crescent, full moon, etc.) are caused by the changing angles of sunlight reflecting off the moon as it orbits Earth.

* Full Moon: During a full moon, the entire sunlit hemisphere of the moon is facing Earth, which is why we see the whole disk illuminated.

So, even though the moon rotates on its axis, the side we see remains the same due to tidal locking.