RSS stands for Really Simple Syndication (also Rich Site Summary) and is a set of XML communication standards. RSS allows web developers to share the content of their site. RSS repackages the web content as a list of data items, such as news headlines, to which you can subscribe either from a directory of RSS publishers or directly from the web sites themselves.
RSS content usually includes news stories, headlines, content from discussion lists, or corporate announcements and is primarily used by news websites and weblogs. RSS "feeds" are generally read with an RSS reader called a content aggregator. There are many RSS readers available for download on the net. Do a search in your favourite search engine for "RSS reader" and you will get a listing of many free or reasonably priced ones.
If you are using an RSS reader and have it set to check your feeds at startup, you will get the latest news and features delivered directly to you as soon as they are available, rather than having to check your favourite web sites each day for updates.
Depending upon the type of reader that you have, subscribing to a feed can be done in several ways. The way which will work with almost any reader is to right click on the RSS or XML graphic normally displayed for the feed, then choose "Copy Shortcut" and paste the shortcut into your reader. Some browsers, including Firefox, Opera and Safari, have functionality which automatically picks up RSS feeds for you. For more details on these, please check their websites.