What is a GIS?
A Geographic Information System, or GIS, is an organized collection of computer hardware, software, geographic data, and personnel designed to efficiently capture, store, update, manipulate, analyze, and display all forms of geographically referenced information. Or, in simple terms:

A computer system capable of holding and using data describing places on the earth's surface.

Many computer programs, such as spreadsheets, statistics packages or drafting packages can handle simple geographic or spatial data, but this does not necessarily make them a GIS. A true GIS links spatial data with geographic information about a particular feature on the map. For example, a polygon that represents a parcel on a map doesn't tell you much about the parcel except its location. To find out the parcel's Council District or Home Owners Association, you must query the database. Using the information stored in the database, you could create a display symbolizing the parcels according to the type of information that needs to be shown.

In short, a GIS doesn't hold maps or pictures - it holds a database linked to different features stored in GIS layers. The database concept is central to a GIS and is the main difference between a GIS and drafting or computer mapping systems, which can only produce a good graphic output. All contemporary geographic information systems incorporate a database management system.

A GIS gives you the ability to associate information with a feature on a map and to create new relationships that can determine the suitability of various sites for development, identify the best location for a new facility, and so on.

GIS Components
A working GIS integrates five key components: hardware, software, data, people, and methods.

Hardware - Hardware is the computer on which a GIS operates. Today, GIS runs on a wide range of hardware types, from centralized computer servers to desktop computers used in stand-alone or networked configurations.

Software - GIS software provides the functions and tools needed to store, analyze, and display geographic information. Key software components are:

• a database management system (DBMS)
• tools for the input and manipulation of geographic information
• tools that support geographic query, analysis, and visualization
• a graphical user interface (GUI) for easy access to tools

Data - Geographic data and related tabular data can be collected in-house or bought from a commercial data provider. Most GISs employ a DBMS to create and maintain a database to help organize, manage, and document data.

People - GIS technology is of limited value without the people who manage the system and to develop plans for applying it. GIS users range from technical specialists who design and maintain the system to those who use it to help them do their everyday work.

Methods - A successful GIS operates according to a well-designed plan and business rules, unique to each operation.