A geographic information system (GIS) is a computer-based tool for
mapping and analyzing things that exist and events that happen on
earth. GIS technology integrates common database operations such as
query and statistical analysis with the unique visualization and
geographic analysis benefits offered by maps. These abilities distinguish
GIS from other information systems and make it valuable to a wide range
of public and private enterprises for explaining events, predicting
outcomes, and planning strategies.
A GIS stores information about the world as a collection of thematic layers
that can be linked together by geography. This simple but extremely powerful
and versatile concept has proven invaluable for solving many real-world
problems from tracking delivery vehicles, to recording details of planning
applications, to modeling global atmospheric circulation.