Summary

Definitions of what a GIS is range from a 'simple' software package designed to acquire, manage, analyze and present geographic information in many ways to a 'complex' computer system including hardware, peripherals, data, software, and applications. A GIS is best defined by the type of questions it should be able to answer:

Location - What is at a given location?
Condition - Where does something occur?
Trends - What has changed since …?
Patterns - What spatial patterns exist?
Modeling - What happens if… ?

Besides the task of answering space related questions a GIS has a number of prerequisites, such as capabilities to import, manage and visualise different data types such as raster and vector data of different origin and different format. One of the most important tasks for a GIS is probably visualisation of information that can be a simple visualisation of spatial relations (the topology) or more complex visualisation of model results or 3D simulations.