Attribute data associated with the layer can be used to symbolise a map. For instance, as previously mentioned, data on vegetation could be used to symbolise a map with a different colour for each polygon area. This would then be able to show which areas of the map represent different types of vegetation based on the attribute data.
The same basic outline layer of a country could be used to create many different kinds of maps depending upon any associated attribute data and the aims of the person creating it. There are many techniques available for customising maps by using symbol functionality. This use of symbology, available within modern desktop GIS, enables the right message to be presented to the target audience.
If you would like to further explore how GIS could help your organisation jps services offers one and two day training courses in QGIS, ArcGIS and MapInfo.