Isoline Map

https://www.e-education.psu.edu/geog486/l6_p6.html

The isoline map, illustrated above, is typically used with continuous lines to join any points of the same value.  Some examples of this might include temperature, barometric pressure, or even altitudes/elevations.  It is used to interpret information and it makes reading a map easier because all the numbers of the same value are grouped together by a line and it is easy to see different contour levels for instance of a geographic area.