Latitude

Geographers use a coordinate system to specify any location on the surface of the earth. One axis of this system consists of lines circling the globe running East and West, called lines, or circles, of latitude. Lines of latitude are sometimes called "parallels", since all latitude lines are parallel with one another.

The best know line of latitude is the Equator, which falls half-way between the earth's North and South poles. 

Another well-known line of latitude is the Arctic Circle (66 1/2 degrees North latitude), the northernmost point where the sun can be seen in Winter, and the southernmost point where the sun doesn't set during the Summer. the Antarctic Circle occupies a similar position in the Southern hemisphere (66 1/2 degrees South latitude).

The other axis in this coordinate system consists of lines circling the globe running North and South, called lines, or circles, of longitude.