A scale is usually found on a map and it shows the relationship between real life dimensions and map projections.
Maps are two dimensional representation of the the three dimensional world. When properly understood we can easily be properly guided and not have problems involving understanding the real life dimensions.
A scale shows the representation factor used in moving from the real world to the map projection.
There are different ways to represent scales on a map. Some use words, others use a bar scale and most maps are written with representative fractions.
