The imaginary lines drawn all over the Earth's surface are called the latitudes and the longitudes. The purpose of these lines are mainly for navigation in aircrafts and satellite geographic locations. Each place in the Earth has a specific coordinates in terms of latitude and longitude. For example, Philippines is located 12.8797° North, 121.7740° East.
Between these two, the imaginary lines parallel to the equator of the Earth are the latitudes. Imagine a Cartesian plane that is revolved about either the x or y axis. You would form a sphere with x and y coordinates. The x-coordinates or the horizontal axis with respect to the equator of the Earth are the latitudes. The vertical axis are the longitudes.