To use a paper map, all you do is unfold it. What you see is what you get. You may see roads, rivers and railroads depicted by different coloured lines. Cities may show up as different sized dots (points) according to their size, and lakes may be areas coloured in a blue pattern. You simply use the map as a tool to interpret a result.
As on the paper map, a digital map created by GIS will have points, lines and areas which may have different sizes, colours, or patterns. The difference is that information about each point line or area comes from a database and is shown only if the user chooses to show it.
The database may store information like where the city is located or how long the road is or even how many square meters a lake occupies.
It may also include attribute data such as the name of the City and when it was established, what the surface of the road is made of and who administers it, or how deep the lake is and what type of recreation occurs on it.
Each piece of information in the GIS map sits on a layer, and the user can turn on or off the layer. Each user may start with a common or base map of streets but the information they add to that map will differ according to their individual needs.
GIS is used to display and analyze spatial data which are tied to databases. This connection is what gives GIS its power: maps can be drawn from the database and data can be referenced from the maps. When a database is updated, the associated map can automatically be updated as well.