An enterprise GIS provides broad access to geospatial data and applications throughout the organization. The advantages to deploying an enterprise GIS include
GIS experts maintain control of the information and applications, yet productivity skyrockets as more users have access to geospatial information. Geospatial information can also be integrated with other enterprise applications to geoenable executive analysis and decision-support systems.

Enterprise GIS is a platform for delivering organization-wide geospatial capabilities while improving access to geographic information and extending geospatial capabilities to nontraditional users of GIS.
What is Enterprise GIS [MP3]
Dave Busser discusses enterprise GIS and what organizations need to know to get started with an enterprise GIS.