In geography and cartology, a map legend, also known as a key, is used to refer to a device used to represent the series of information contained in a map. A legend or key comprises symbols, lines, patterns, etc. used to represent what is shown on a map.
A map legend is used to represent the information on the map in order for any reader to decipher it. The legend is written alongside a short description of what each symbol, line, etc. represents.
For example, a series of convoluted lines may be used to represent mountains or mountainous terrains.