The latitude and longitude lines allow someone to supply their coordinates anywhere on earth. Latitude lines go from east to west while longitude lines go from north to south.
The latitude lines center on the equator, since the equator represents the halfway point between the North Pole and the South Pole.
The lines of longitude revolve around Greenwich, England, which is also referred to as the prime meridian. Greenwich, England gets to be the prime meridian because when longitude and latitude were established, Great Britain was arguably the most dominant country in the world.
To find the place of something on the globe, measure how far away it is from the equator and the prime meridian. The answer will be given in degrees, with latitude first and longitude second.