A portlet is information that is placed within a region on a page. All portlets come from a data source registered with Oracle Portal, called a portlet provider. Portal itself is a portlet provider, because certain aspects of the product have been made available so that you can include them on your own pages. This snapshot of the Portal Builder page, for example, shows three portlets, all from Portal:
By selecting the appropriate Portal portlet provider, you can place
any of the portlets shown in this snapshot on your own pages. Portal
also provides other portlet providers so that you can make most
Portal objects available to your pages as well. To see the complete
list of objects you can place in a region, click 
while editing a page.