Here is an example of a chloropleth. Chloropleths give different regions a color thats affiliated with some type of data. one of the most common examples of this is showing which states voted for a certain presidential candidate during the election.
A dot density map is exactly what it sounds like. A dot is placed on the map for each incident for some type of data. A common example is a population dot density map, where each dot represents an allotted number of people.
Proportional symbol maps provide an visual representation of the magnitude of a statistic for a region. The larger the symbol, the larger the number.
Lastly, an isarithmic map shows how a certain type of data varies over a region. It is displayed by change in color and its shape is not limited by the political lines drawn on maps.