This page is made up of different "windows." There is one window for the weather update, another window for news, a third for a stock price update, and so on.
Each of these windows represents a portlet.
Under the covers, these windows are different applications, developed independently of each other.
The developer of the news portlet will create an application and pack it into a .war file. Then the administrator of the portal server will install this .war file on the server and create a page. In the next stage,
every user will choose which applications he wants on his page. For example, if the user is not interested in stock updates but is interested in the sports update, he can replace his "Stocks Update" window with a "Sports Update" window.