For thousands of years humans have developed ways to take our three dimensional world and project it onto the two dimensional context of a map. Mapping and cartography have enabled us to better make sense of where we are in the world and in understanding our geographic positioning in relation to everything else on the planet.
"The parallels and meridians form a grid system on the model of the Earth. The grid serves as a reference system for locating points on the surface of the Earth. In the map projection transformation process, this grid system is transferred to the map". (Pearson, 1990, p.20)