Portlet

Portlets are pluggable user interface components that are managed and displayed in a web portal. Portlets produce fragments of markup code that are aggregated into a portal page. Typically, following the desktop metaphor, a portal page is displayed as a collection of non-overlapping portlet windows, where each portlet window displays a portlet. Hence a portlet (or collection of portlets) resembles a web-based application that is hosted in a portal. Portlet applications include email, weather reports, discussion forums, and news.

Portlet standards are intended to enable software developers to create portlets that can be plugged in any portal supporting the standards. (-> en.wikipedia)