Hi, Well Portal Technology is nothing but a set of portlets forming a portal application. Now these portlets are extension of Servlets. WebSphere have its own set of Portlet Api's. The purpose of all the above stuff is that a user interface can be customized easily through a portal server. So the basic punch line is portlets are extension to servlets.A single page can have multiple portlets . Also an administrator can set access rights on the portlets ,pages etc.
Hope this helps else find more information on IBM Site for Websphere Portal 5.0
SCJP1.4<br />IBM Certified System Administrator -- WebSphere Application Server V5.0 (340)
>>Well Portal Technology is nothing but a set of portlets forming a portal application. << I would add a portal is a framework. It also typically happens to be a web application that runs in servlet container. The portal framework allows for the aggregation and integration of content from various sources. Another strength is the ability for the user to sign-in once then have access to the various content sources without having to authenticate for each source.
Portal applications are created to run in the portal. Portal applications can be suites of portlets. There is now a defined standard for portlets: JSR-168. Most of the vendors, if not all, are now supporting or providing compliance with this standard, such that a portlet written to the JSR-168 standard will run in all compliant portals.
Some, but not all portal vendors will provide additional functionality beyond the JSR-168 specification. For example, the JSR-168 specification does not provide for inter-portlet communication.