Thematic mapping is the process of shading your map according to a particular theme. The theme is usually some piece or pieces of your data, which is obtained from a dataset. Themes present your data visually with shades of colour, fill patterns, symbols, or bar and pie charts. You create different thematic maps by assigning these colours, patterns, or symbols to map objects according to specific values in your data. Bar and pie charts allow you to make data comparisons for each record in your dataset.
Thematic mapping also allows you to discover trends in data that would be difficult to see through tabular data.