Choropleth Map

A choropleth map is a map that is color-coded by zones, used to distinguish different pieces of data. A popular example is an election map, which often color-code states based on the voting population. A goof choropleth map contains a legend and scale bar, and many require having the North arrow somewhere on the map to establish direction.  For instance, this map compares how many males reside in each state compared to 100 females.
Source: http://my.ilstu.edu/~jrcarter/Geo204/Choro/