A geographic information system, or GIS, is a way of collecting, storing, and displaying data rooted in geographic space and time. Usually the way people interact with this system is by either adding collected data to a system or by using the system to draw conclusions about the real world. Many different professions interact with GIS in different ways to achieve different ends, but this type of system is particularly useful in professions that need detailed geographically oriented data, such as geology. The quality of the system is almost entirely dependent on the quality of the data, which is in turn dependent on the skill of the people collecting the data. While the hardware and software involved in the system are also very important, the actual data is the heart of GIS.
GIS can be used to map all kinds of different data, including topographic, demographic, and simple geographic data. At its most basic, GIS is a mapping system that can be used for cartographical purposes. In general, though, people using this type of system have additional data that is used. That data is tied to a space and date of recording and can be used in all kinds of applications depending on the subject.
In the very least, this type of system requires an ordered way of determining where things are. For every relevant geographic point that exists, a point must exist in the mapping system. Since something different may exist at every point over time, it is important for this kind of system to be updated frequently.
This concept of tying information to a place can be difficult to understand in the abstract but is very clear in reality. For example, if the police were studying patterns of crime in a particular city, they might use a map of police incidents to visualize where crime usually occurs and place officers accordingly. If the data used in that application were to include the type of offense, the age of the offender, and the time, a person interested in the relation between school hours and youth involvement in drug crimes might be able to make a compelling argument that children should be kept in school longer if the data supported that claim. The point is that GIS is not only useful for information about geographic features. Everything in the human world occurs at both a place and a time, and therefore GIS can be used as a valuable tool to make sense of most everything in the human world.