A choropleth map is a thematic map in which areas are shaded or patterned in proportion to the measurement of the statistical variable being displayed on the map, such as population density or per-capita income. The choropleth map provides an easy way to visualize how a measurement varies across a geographic area or it shows the level of variability within a region.
An isoline map is a map with continuous lines joining points of the same value. Examples would be equal altitude (contour lines), temperature (isotherms), barometric pressure (isobars), wind speed (isotachs), wind direction (isogon), wind shear (isoshear), etc. Isoline mapping is used to interpret the information on some thematic maps.