The Moon appears to change shape because we see different amounts of the lit part as the Moon orbits Earth. From Earth's perspective, we see varying amounts of the illuminated part of the Moon.
Geographers use map projections to translate the planet in a two dimensional representation. Unfortunately, you can’t display 3D surfaces perfectly in two dimensions, distortions always occur. There are many different projections that are commonly used throughout the world.
By rename do you mean turn into an improper fraction?
if so, it is because without turning it into an improper fraction, you cannot subtract 3/4 from 1/4 because you would get a negative answer and that would be incorrect
Bureau of Land Management, Fish and Wildlife Service, Forest Service, and National Park Service