Answer:
The symbol of a map are explained in its legend or map key.
Step-by-step explanation:
Map key provides additional information to better understand the map. Not all information can be included in the actual map, therefore, the map key serves this purpose. It is normally written in a box and positioned at the corner of the map.
Compressive maps use different colors, have different feature representation, etc. Symbols which are sometimes pictures or icons used for different purposes are further given an explanation on the map key. It sometimes contains scale representation.