Geographical Latitude

How do circles of latitude and longitude specify one's location on the surface of the earth? 

What is the latitude and longitude of your home town?

Terrestrial latitude measures one's distance north or south of the equator. The largest latitude circle is the equator itself, which is zero degrees. Other latitude circles are parallel to the equatorial plane, and grow smaller nearer the poles. In each case the latitude north or south of the equator is measured in degrees, and is equal to the angle between a point on the equator (E), the center of the earth (C), and the location of the observer (O; latitude = angle ECO).