What is RSS?
Before you go any further, realize this: RSS is really simple. Just because it is an acronym doesn't mean that it's complicated. Don't get scared away, there's really nothing to it. Depending on who you ask and what version of RSS is in question, RSS may stand for Really Simple Syndication, Rich Site Summary, RDF Site Summary, or a variation on one of those. None of that matters to you anyhow. Another thing that you don't need to care about is the versions. There are 0.90 and 0.91 (created by Netscape), 1.0 (by RSS-DEV), and 0.9x and 2.0 (by UserLand Software) versions, but almost all applications that handle RSS feeds can read all the different versions.
RSS is a text-based format, a type of XML. You should know that only because often RSS files are often labeled as XML. RSS version 1.0 is also RDF, which, again, is important only because an RSS file may be labeled as RDF. RSS files (which are also called RSS feeds or channels) simply contain a list of items. Usually, each item contains a title, summary, and a link to a URL (e.g. a web page). Other information, such as the date, creator's name, etc., may also be available. The most common use for RSS files is for news and other reverse-chronologically ordered websites like blogs. An item's description may contain all of a news article, blog post, etc., or just an extract or summary. The item's link will usually point to the full content (although it may also point to what the content itself links to).
When a website has an RSS feed, it is said to be "syndicated". There are various other syndication formats besides RSS (such as Atom), but RSS is by far the most widely used and supported today. RSS files do not have a common file extension, although they frequently end in one of .xml, .rss, or .rdf (note that other extensions may be used also). The term "scraping" refers to creating an RSS feed for a website that doesn't provide one itself (i.e. scraping the text off of the page). That is, scraped feeds are not created by the same people who created the content within the feed. Scraped RSS feeds may stop working if the page changes its layout.