I think in this case Wikipedia have it right
Windows SharePoint Services (WSS) is the basic part of Microsoft SharePoint, offering collaboration and document management functionality by means of web portals, by providing a centralized repository for shared documents, as well as browser-based management and administration of them. It allows creation of Document libraries, which are collections of files that can be shared for collaborative editing. SharePoint provides access control and revision control for documents in a library.
In a nutshell Sharepoint is all about corporative management and collaboration features. Your company have a Windows 2003 server? Here you go. WSS 3.0 is here up and running.
