Depending on who you ask, it stands for “Rich Site Summary,” “Really Simple Syndication,” or “RDF Site Summary.” Regardless of the acronym, it’s actually a very straightforward technology: whenever a website publishes new content, that content can automatically be put into an RSS feed.
Best of all, you can use an RSS newsreader (a bit of software) to quickly and easily check your favorite web sites to see what is new. "Your favorite web sites" might include news sites, the latest stock market prices, weather forecasts, just severe weather updates, your genealogy society's web site, a list of upcoming satellite launches, updates on airline flight prices, some job-search websites, a certain genealogy newsletter (ahem!), Hollywood gossip sites, or if you’re especially interested in one particular topic you can easily and quickly see what is new on that site. The sky is the limit.
HINT: The RSS newsfeed for Eastman's Online Genealogy Newsletter is: https://eogn.com/page-18080/rss
You don't use a normal web browser to read RSS news feeds. Instead, you use what is known as an RSS newsreader. That might be software that you install in your computer or you can use an RSS newsreader that is in the cloud (which means you don't have to install anything).
You can get web-based, desktop, mobile, and even browser add-on RSS newsreader versions, most of which let you subscribe to up to 100 sites before asking you to pay to upgrade your membership to access more features. There are dozens out there, but the following are a great place to start.
Feedly (my favorite web-based RSS newsreader (no software installation required!) plus Android and iOS versions are available) at https://feedly.com.
InoReader (Web-based plus Android, iOS, and Windows Phone versions at https://www.inoreader.com/).
NewsFlow (for Windows only) at https://apps.microsoft.com/store/detail/newsflow/9NBLGGH58S5R?hl=en-us&gl=US.
RSSOwl (Completely free for Windows, macOS, and Linux) at http://www.rssowl.org/.
NetNewsWire (completely free for Macintosh or iOS only) at https://netnewswire.com/.
Awasu An advanced RSS newsreader but for Windows only) at https://awasu.com/products.php.
Feeder (an add-on for the Google Chrome, Mozilla Firefox, and Microsoft Edge web bowsers plus free-standing apps are available for iOS) at https://feeder.co/
There are dozens more RSS newsreaders available but the above list is some of the more popular ones. I'd suggest you start with one of the above. It is possible that you will want to switch later to something else once you gain experience with the advantages of RSS,
RSS remains one of the best ways to make sure you see everything your favorite sites publish. It also allows you to check dozens of web sites much more quickly and easily than visiting each web site one at a time with a web bowser.