Why do flat maps distort either the shapes or areas of land masses?

The size, shape, and relative location of land masses would change. Projection is a major challenge for cartographers ... For example, conformal maps show true shapes of small areas but distort size. Equal area maps distort shape and direction but show true relative sizes of all areas.

Be cause if a map were to me put in a circle it would create a cylinder, which i hope you know the world is not