The document discusses RSS (Really Simple Syndication) and how it can be used to aggregate content from various sources on the web. It defines key aspects of RSS like syndication and how RSS feeds can be found and added to an RSS reader. It provides examples of how RSS can be used to receive automatic updates from PubMed searches and other sources like library blogs and databases. The document also mentions that RSS feeds can be exported and imported between different RSS readers using the OPML format.