What is a Projection?
A map projection is a method for taking the curved surface of the earth and displaying it on something flat, like a computer screen or a piece of paper. Map makers have devised methods for taking points on the curved surface of the earth and "projecting" them onto a flat surface. These methods enable map makers to control the distortion that results from creating a flat map of the round earth.
Every map projection has some distortion. Equal area projections attempt to show regions that are the same size on the Earth the same size on the map but may distort the shape. Conformal projections favor the shape of features on the map but may distort the size.