According to wikipedia "Sharepoint is a browser-based collaboration and document management platform from Microsoft."
The word sharepoint refers to both Windows Sharepoint Services 3.0 (WSS) and Microsoft Office Sharepoint Server 2007 (MOSS).
Windows SharePoint Services 3.0 (WSS)
1. Used for storage and web presentation.
2. Authorization/user management.
3. Interface to WWF (Windows Workflow Foundation).
4. APIs (Application Programming Interfaces) & web services that can be extended by developers.
5. Collaboration tools and functionality.
For more info on WSS
Microsoft Office Shareoint Server 2007 (MOSS)
MOSS comes in 2 versions - MOSS 2007 Standard and MOSS 2007 Enterprise.
MOSS 2007 Standard (provides all functionality available in WSS with the below mentioned features)
* Portal templates for building your internet/intranet site.
* User profiles, social networking and my sites.
* Web parts for aggregating information.
* Enterprise search.
* Web content Management (WCM).
* Additional built-in workflow templates.
MOSS 2007 Enterprise (provides all the functionality available in standard version, with additional features)
* BDC - Business Data Catalog
* Forms Server
* Excel Services
* Additional Web Parts