Longitude indicates distance from the prime meridian, whereas latitude indicates distance from the equator, and these measurements cross one another rather than being equivalent. These lines are depicted on maps as a grid crossing the entire surface of the Earth.
Lines of longitude are used to indicate distance east or west of the prime meridian. This is a line that passes from the North Pole through Greenwich, England, to the South Pole. On maps, it is sometimes written as 0. For every 15degrees east or west of the prime meridian, a new line of longitude is drawn on the map. They converge at 180 degrees in the middle of the Pacific Ocean and overlap at the International Date Line.
Lines of latitude start at the equator, crossing through Quito, Ecuador. Every ten degrees north or south, a new line of latitude is drawn. At the poles, they are written as 90 degrees north or 90 degrees south.
For extra precision, such as that used in a GPS, degrees can be separated into minutes and seconds. A minute is 1/60 of a degree, and a second is 1/60 of a minute. On a map, coordinates are written latitude first, then longitude.