If you're new to SharePoint, or working with people who are new to SharePoint and have a hard time explaining what it is, you might find the SharePoint in Plain English video to be helpful.
This video takes a friendly approach to show how SharePoint can help you work together with others in more efficient ways. For example, SharePoint can help you plan and work on a project online instead of sending files back and forth in e-mail.
Link to the video: http://www.microsoft.com/video/en/us/details/76e8d3af-c2bd-42a6-bb12-befcbd041bf1
