latitude/longitude

Longitude lines (example in blue at right) run north-south and meet at the North and South Poles; they are also called meridians.  Longitude divides the Earth's surface into 360 thin slivers of one degree each.

Latitude lines (example in red at right) run east-west and don't meet. For this reason they are also called parallels.  Latitude divides the Earth's surface into 180 thin rings of one degree each.

These divisions and their numbering are easier to see if you map the Earth as a flat sheet instead of a sphere. In the sphere to the right and in the flat map below, the lat/long gridlines are drawn five degrees apart.