GIS is a computer system for capturing, storing, checking, integrating, manipulating, analyzing and displaying data related to positions on the Earth's surface.

Typically, a Geographic Information System is used for handling maps of one kind or another. These might be represented as several different layers where each layer holds data about a particular kind of feature.

Each feature is linked to a position on the graphical image on a map and a record in an attribute table. GIS can relate otherwise disparate data on the basis of common geography, revealing hidden patterns, relationships, and trends that are not readily apparent in spreadsheets or statistical packages, often creating new information from existing data resources.

Hidden in most data is a geographical component: an address, postal code, census block, city, county, or latitude/longitude coordinate. With GIS, you can explore the spatial element of your data to display soil types, track crime patterns, analyze animal migration patterns, find the best location for an expanding business, model the path of atmospheric pollution, and make decisions for many types of complicated problems.

ESRI maintains a list of GIS uses by industry

Architecture

• Integrate AutoCAD and MicroStation files with GIS data.
• Explore the environmental impacts of various landscape architecture projects

Business

• Site selection projects
• Real estate analysis of housing market

Computer Science & Engineering

• Use geospatial engines and libraries to help automate geographically aware processes.

Geology

• Analyze relationships between rock, soil, vegetation types.
• Analyze oil/gas deposits and determine extraction points.

Nursing

• Epidemiological analysis
• Determining suitable access to health care

Reserve Officers' Training Corp (ROTC)

• Analyze the geographic distribution of resources and personnel
• Integrate and interpret remotely sensed imagery into maps and plans

City & Regional Planning

• Landuse analysis
• Transportation/network analysis

Social Work

• Community assessment projects