RSS stands for Really Simple Syndication...aka a means to read the subscribed content on a "reader" of your choice. This tool allows one to pull in articles from their favorite authors, websites, forums, blogs and read them in one place. Kinda like creating a daily briefing book. Keeps you current with your favorite topics without having to visit each and everyone separately.
You can do this on your computer or with the right smart phone in the palm of your hand anywhere in the world.
The drawback, you don't discover other threads and posts you get exposed to when you visit the forum or website.