A Web Part, also called a Web Widget, is an ASP.NET server control which is added to a Web Part Zone on Web Part Pages by users at run time. The controls enable end users to modify the content, appearance, and behavior of Web pages directly from a browser. It can be put into certain places in a web page by end users, after development by a programmer.
Web Parts can be used as an add-on ASP.NET technology to Windows SharePoint Services.
Web Parts are equivalent to Portlets, but don't necessarily require a web portal such as SharePoint to host them.
See also Portlet Web widget ASP.NET Windows SharePoint Services SharePoint Portal Server Microsoft Office SharePoint Server 2007 Microsoft SharePoint 2010
References
External links ASP.NET Web Parts Controls
he:SharePoint#Web part