This map uses Robinson projection. But what is a robinson and what is projection? Well, lets start about what a projection actually is...
Map projection. Map projection is a way to represent the globe which is an inperfect sphere, onto a flat survace. (For example a large piece of paper or the screen you are currently watching ;-)) And why? Well in order to get a useable map. And that last part, well that is the hard part. You have to deal with the practival use of maps (navigation, geograpgical shapes, distance between objects, etc) as well as very complicated mathematical problems about how to shape the world. As you must surely understand, there is not one answer to this problem. Any 2D projection of the world will always distort the reality in some smaller or larger way. Because every problem has it's own solution, there are numerous amounts of projections. Each was developed to minimize the disortion for that specific use. Some are very famous, some you will probably never have heard from. Maybe click around the globe on mapclicker and find the obscure one you where looking for.
The Robinson projection was presented in 1963 by Dr. Arthur H. Robinson. He was a professor of geography and cartography at the University of Wisconsin from 1947 until he retired in 1980. The map he created was made by request of a commercial atlas publisher. Dr Robinson experimented with by changing the vertical and horizontal scales using a table. He kept refining the variables until he found it aesthetically pleasing.
"I started with a kind of artistic approach," Dr. Robinson said in a 1988 interview in The New York Times. "I visualized the best-looking shapes and sizes. I worked with the variables until it got to the point where, if I changed one of them, it didn't get any better."Quite the exception when most projections are based on mathmatical formulas. More information including the projectiontable can be found here: Indept Robinson explaination. Did you know that the National Geographic Society used the Robinson projection as it's default projection for world maps between 1988 and 1998.