A moon is an Earth's natural satellite which we view virtually every night. It guarantees that its moon travels in a predictable path around the Earth. When the moon orbits the globe, the gravitational force between the planet and the natural satellite maintains it in place.
The full moon or Paurnima occurs when the moon body is behind the earth and sun and we can view the complete lit area.
We could only view the black part when it is between the sun and the earth, and a new moon, or Amavasya, occurs. We witness intermediate phases such as a half-moon and crescent between these two extremes.
Hence, the full form of the moon is “Poornima or Full moon night”.