Portals
In its most general definition, a portal provides a point of entry to a data collection that has been collected and organised according to audience needs. The term is used widely and in different ways, and a service describing itself as a portal may provide entry to extensive collections of databases or simply offer a list of links to other relevant sites. Other terms that have been used to describe this type of service include: gateway, subject gateway, digital library, clearinghouse, and Internet resource guide.
For a detailed discussion of definitions and types of portals refer to Londsale, M. (2003) Global Gateways: a guide to online
knowledge networks 3rd ed, education.au limited/ACER.
http://www.educationau.edu.au/jahia/webdav/site/myjahiasite/shared/papers/global_gateways_v3.pdf
What distinguishes portals from static websites is their ability to incorporate data from multiple sources in multiple formats, yet organise it in a consistent way and provide integrated access within a browser.
Many portals also offer value-added services such as email, web page hosting or filtered information flow. Increasingly portal architecture standards also support personalised features, such as user profiling and single sign-on and point of entry to multiple collections of distributed resources or databases; and may offer different content for different users.
Portlet
Portlets or portal applets are "web components, managed by a portlet container (portal), that process requests and generate
dynamic content" in response to a particular user. Usually multiple portlets are invoked to create a personalised web page.
(Source: http://www.javaworld.com/javaworld/jw-08-2003/jw-0801-portlet.html)
Portlets rely on APIs to access various types of information, such as user profile. Portal server vendors have tended to define
proprietary APIs for local and remote portal components creating interoperability problems for portal customers, application
vendors, content providers and portal software vendors.
(Source: http://www.nwfusion.com/details/666.html)
The goal of portal standards is to rationalise the way portlets interact with the portal software itself. Standardising this interface allows portlets created in different development environments to operate predictably with any standards-supporting portal. This simplifies the process of designing and coding what the portal needs to see from the portlet and vice versa, and thus assists content providers.