Contour maps depict spatially-varying values, such as elevation, by means of curves of equal value.
A contour represents all points where the value of a function is a constant. Collections of contour lines, or contour maps, are often used to depict spatially-varying functions, typically elevation.
Questions tagged with "contour" typically pertain to the construction, interpretation, or processing of contour maps.
Synonyms include "contour line", "isoline," "isarithm," "level set," "isocontour," and "implicit curve." In specific applications, where the function in question has a conventional meaning (such as pressure, temperature, etc.) contours are often called "iso-X" where "-X" is related to a Greek or Latin name for the same quantity; e.g., "isobar" ("equal pressure") and "isotherm" ("equal temperature").