Flow map

http://mundi.net/maps/maps_014/

This is a flow map because it maps the travel or "flow" of something across the globe. Flow maps are very useful in all aspects of todays modern world, because of the ability to track so many different variables that travel across countries borders. This specific flow map is showing telephone traffic in Europe. As you can see countries that talk on the phone more have thicker, bolder lines traveling between one another, while less telephone traffic has thinner, skinny lines between them.