A Geographic Information System (GIS) is a specific piece of computer software that, like a database program, allows the user to store, maintain, analyze, and display database information. What makes a GIS different from other database systems is that the information managed has a geographic or spatial context.
Based on the common denominator of geographic location, GIS ties data from many different sources into 1 common map form. This allows the user to visualize the data and see how the different data interact, resulting in a better understanding of the information and a more informed decision process.