Take an orange and draw something on it -- say, a human face. Now carefully remove the peel, trying to keep it in one piece, and flatten it against your kitchen table. You'll see that in making a two-dimensional object out of a round one, something has to give. Either the face gets distorted and looks all 'mushed out,' or in flattening the peel, it breaks into segments, dividing the face as well into several parts. A cartographer chooses between a series of those kind of lesser-of-two-evils alternatives.