RSS (most commonly translated as "Really Simple Syndication" but sometimes "Rich Site Summary") is a family of web feed formats used to publish frequently updated works—such as blog entries, news headlines, audio, and video—in a standardized format.
They benefit readers who want to subscribe to timely updates from favored websites or to aggregate feeds from many sites into one place. RSS feeds can be read using software called an "RSS reader", "feed reader", or "aggregator", which can be web-based, desktop-based, or mobile-device-based.
Your Firefox browser is capable of reading RSS feeds and displaying them as "Live Bookmarks" which update periodically and show the listed items when you open them.
Google Chrome has a similar Chrome Feed Reader app that can display the feed from your toolbar.