A map is any sort of an organized representation of a given physical space.  Maps typically try to show relevant aspects of the actual physical space that they represent on a much smaller scale.  Maps can show a variety of things.  Maps can show where streets run in a city.  They can show where certain physical features such as mountains and rivers are.  They can show what areas of the world make up the territories of the various countries. 

Maps are very important because of the information that they can impart to us.  For example, a road map is very important for a person who is trying to travel in an unfamiliar place.  The road map can help that person know where they are going and plan out alternate routes to get to that destination.  As another example, a topographical map can show a civil engineer where the best place to put a road would be.  The engineer can look at the map and see what route would be easiest to build.  At the same time, though, that engineer might want to look at another map that shows land ownership.  The engineer might have to consider both the topography and who owns the land when considering where to put the road.  Basically, anyone who wants to be able to look at the ways in which various things are spread out across a given physical area can benefit from using a map.