Cartograms

Cartogarms are maps in which there is a substitution of variables, usually mapped thematically. For example if you wanted to show the relative size of U.S. capital cities based on their populations you can distort the size of the city to reflect its actual population. So that Tallahasseee would appear smaller than say Austin TX. Cartograms come in two classes. They are either area cartograms or distance cartograms. Distance cartagrams are used to show distances and time in between verticies.

Link: http://haleysmaps.blogspot.com/2011/04/cartogram.html