Lines of latutude are circles drawn on the Earth parallel with the equator. Lines of Longitude are imaginary vertical lines perpendicular to the equator. Latitude and Longitude are given as angles. Lines of Latitudes go from 0 Degrees at the equator to + 90 degrees or 90 degrees North at the North Pole and - 90 Degrees or 90 degrees South at the South Pole. Lines of Longitude increase from 0 Degrees to 180 degrees from a vertical line through Greenwich, in London England, and are labelled either Eat or West.
In this way every point on the Earths surface can be labelled uniquely by the two angles - given in degrees, arcminutes and arcseconds - of latitude and longitude.