RSS stands for Really Simple Syndication.  It's a system whereby a web site, like this one, can create a newsfeed of the articles on the site.  This newsfeed is like a constantly updating list of the latest articles.  If you monitor the newsfeed, you can have copies of the articles available to you without having to visit the original website.

In order to do the above you would need a News Reader. There are many different versions, some of which are accessed using a browser, and some of which are downloadable applications. All allow you to display and subscribe to the RSS feeds you want.