GIS stands for "geographic information system" and refers to any system that accumulates organizes and analyzes data as it relates to geographical location. GIS includes computer software capable of taking in data from land surveys, aerial photographs, satellite pictures and other sources, and then taking this data and representing it in geographical form.

Thus, by combining many layers of information about a particular place, a GIS can provide its user with a better understanding of said place. These layers of information might include landmarks such as rivers, mountains or streams; or it might be civil infrastructure data, like roads and highways. The location of restaurants and gas stations might also be fed into a geographic information system. The nature of the data one inputs into a GIS depends on what kind of analysis one is trying to get. For example, if you want to visually map what areas of the city are more crime ridden, you can input recent crime statistics and get a visual map of them in a GIS from which you can then derive certain patterns. The same can be done when analyzing the extent of environmental damage in a particular place, of to decide what area has the best demographic for particular kinds of businesses to flourish in.

GIS analysis is possible only because most sets of data contain some form of geographical reference: zip code, city, country, address, etc. The digital maps displaying the information contained in GIS software are dynamic, and can be modified at any time by adding or removing criteria from the data input. This lets users see how each set of data affects the two-dimensional map model.

Future Uses
GIS technology has been typically used by corporations and governments to analyze demographical statistics or to illuminate patters in certain industries, like real estate, as they relate to geographical locations. But with the ever increasing portability and power of personal computers as well as the unprecedented growth in the popularity of the iPod and the use of GPS navigation systems in cars, the biggest expansion in the use GIS technology will most likely be in the sphere of consumer electronics. The location based services (LBS) provided by GIS technology are already letting consumers pinpoint their location on their GPS or GPS-enabled phones as it relates to the nearest points of interest, like restaurants, bars, bus stations, etc.

As the mobile technology products arise, GIS mapping becomes integrated more and more in consumer electronics. There is a good article on geospatial database that shows how this GIS technology works.