Anything on earth can be represented in a GIS as a feature:
Course map BEFORE features
Course map with POLYGONS
Course map with POINTS
Course map with LINES
Every feature in a GIS map has a record in a table linked to it. For example, a sewer pipe (represented by a line) can have information about its length, diameter, flow rate, most recent maintenance, or an endless list limited only by the user’s needs. These are known as a feature’s attributes. In the map you can highlight (select) a feature, open up the table, and examine all the information related to it. Or you can select a record in the table to see where the feature is on the map.
The tables behind the features enable a GIS user to find information about them and display the results on a map by performing queries. Like which towns are over 30 square miles in size?
Or which towns have over 10,000 households?
A GIS user can also query features based on their location in relation to other ones-what is near what, how many are in that one, how close is this to that, and so on. For example, which towns have golf courses within their borders?
Features can be classified by the data in the attribute tables and displayed in thematic maps. For example, a dot density map of population:
Or in a map showing the same results a different way, the darker the color the higher the density:
GIS isn’t limited to flat maps and databases. There are many extensions to the basic software packages that enable things such as three dimensional visualization and analysis and much more.