What is GIS?
http://www.gis.com/whatisgis/index.html

The Guide to Geographic Information Systems, Environmental Systems Research Institute (ESRI)


This site presents an overview of modern GIS (geographic information systems), how these systems work, and how they are used. The site includes a geography network and a map book gallery, and is most easily navigable from the site map.

This resource is referenced here:
Subject: Geography:Geospatial, Geoscience:Geology
Resource Type: Scientific Resources:Overview/Reference Work, Audio/Visual:Maps, Images/Illustrations
Topics: Earth surface