GIS stands for "Geographic Information Systems".
Still confused? Well, to put it more simply a GIS is mix of specialized computer mapping software, geospatial data that links locations with information about those locations, and the people who use software and data to map and analyze real-world situations.
GIS is a mapping technology that allows the user to create and interact with a variety of maps and data sources. GIS displays, analyzes, stores, and manages geographic information.
GIS can give a better understanding of a place and what is happening in and around that place. For instance, GIS can give numerous amounts of information about a piece of property... Who owns it; What town it is located in; What school district it is in; What street it is on; How many people live there; and so on!
GIS has no limits as to how it can be utilized. It can be employed on a local or global scale and can give information for many purposes such as: tax assessment, planning, emergency management, environment, transportation, marketing, education, and many more.
So in many ways GIS is an entity which can produce high tech maps with much more detailed information then could ever be placed on a single map. Unlike a paper map, which only has the ability to show a limited amount of information, GIS can combine many layers of information. Oh yes, GIS can produce those nice, vivid maps that are needed to display particular information, but it is much more than that. GIS can analyze and discover hidden relationships; and it can even provide answers to "what if" scenarios.