Maps are in use throughout the world. Most of these maps can be placed into one of two groups: A) reference maps; and, B) thematic maps.
Reference maps show the location of geographic boundaries, physical features of Earth, or cultural features such as places, cities, and roads. Political maps, physical maps, road maps, topographic maps, time zone maps, geologic and Physical maps, and zip code maps are all examples of reference maps. Since Ptolemy created his first map a variety of reference maps have been created for almost every country of the world.
Thematic maps show the variation of a topic (the theme) across a geographic area. Weather maps showing daily high temperatures across the United States are familiar examples of a thematic map. They are made by starting with a reference map of the United States. Then temperature data is plotted atop of the reference map using colors to communicate the temperature forecast. Income maps and resource maps are other types of thematic maps.
New collecting fields
When we started selling maps some 45 years ago the main focus of the collector and general map buyer was on the standard early maps from the 16th to 18th century created by Ortelius, Blaeu, Hondius, Mercator, Sanson, etc. Soon the collector discovered the figured border maps, followed by Road- and Post Road maps, Geological maps.
Very recently we have seen a boom in the fields like Pictorial maps and not to forget Persuasive maps of which the P.J.Mode collection is the most important.