What is RSS and XML?

An RSS (Rich Site Summary, Really Simple Syndication or RDF Site Summary) feed is defined by wikipedia as a family of web feed formats used to publish frequently updated content such as blogs, news feeds and podcasts. In other words an RSS is a format for delivering regularly changing web content. Many news-related sites, weblogs and other online publishers syndicate their content as an RSS Feed to whoever wants it. An example of an RSS feed can be seen in the side bar of this page, which links the user to any recently updated information added to my del.icio.us account (see below). For more information on RSS feeds, how they are used and why, see whatisrss.com

XML stands for Extensible Markup Language and its primary purpose is to facilitate the sharing of data across different information systems, particularly via the Internet. XML is used for documents containing structured information. Structured information contains both content (words, pictures, etc.) and some indication of what role that content plays (for example, content in a section heading has a different meaning from content in a footnote, which means something different than content in a figure caption or content in a database table, etc.). Almost all documents have some structure. A markup language is a mechanism to identify structures in a document. The XML specification defines a standard way to add markup to documents.
For more information visit O'RiellyXML.com