A portlet is a pluggable user-interface software component that is displayed in a web portal (such as an enterprise portal or a web content management system).
A collection of portlets produce fragments of markup (such as HTML, XHTML, or WML) that are presented as an integrated portal user experience.
A portlet container owns a collection of portlets.
Portlet-based applications are often used for portals focused on news, weather,
Its container sends data to the portal for aggregation, but is not responsible for aggregating the content produced by the portlets. The portal itself handles aggregation.