Here are two good introductions to GIS. The first is a series of videos from Pennsylvania State University called Geospatial Revolution. This four-episode series explores how geospatial technologies, including GIS, are changing our world for the better, and how new jobs are being created in this industry.
Trailer Video
Episode 1
Episode 2
Episode 3
Episode 4
Additional Resources
Another great resource is Esri's "What is GIS"? This is a more detailed introductory look at what GIS is, and how it fits within the larger geospatial world. This site includes interactive demos that allow you to solve some real-world problems using GIS.