The geographic grid is a system designed to pinpoint any location on Earth by laying a vertical and horizontal grid over the Earth's layout. The vertical lines are called the longitude and the horizontal lines are the latitude. The intersection of these two points determines any exact location.
The geographic grid is fundamental to the study of geography because its medium of communication relies so heavily on the use of maps. The lines are a man-made invention based off the location of the north and south poles.
Latitudinal lines measure degrees north to south, with 0 degrees being the exact halfway point between the north and south poles. Longitudinal lines measure degrees east to west, running vertically between the north and south poles.