RSS (which stands for, among other things, Really Simple Syndication) that allows you to syndicate your site content. It defines an easy way to share and view headlines and content through newsfeeds. You can find RSS feeds in hundreds of thousands of places on the Internet which allow you to stream their articles into RSS readers - or your Joomla site.

The Feed Display module allows you to display other sites’ RSS feeds on your site, which is a great way to keep your content from being static.

Search-engine friendly URLs. Refers to URLs that are descriptive in a way that search engines can understand. Normal Joomla! URLs look something like this: http://www.yoursite.org/index.php?option=com_content&view=section&id=3&Itemid=41

You can optionally have URLs display to look like static HTML pages like this: http://www.yoursite.org/faq.html

Joomla! 1.5 has built-in optionos for SEF URLs. These are enabled by changing the ""SEO Settings"" in the Site tab in the Global Configuration screen in the Joomla! back-end. There are also third-party extensions that create SEF URLs for Joomla!.

Reference: http://docs.joomla.org/Glossary