RSS (Really Simple Syndication) allows the website to let you know every time that it is updated. It provides you a method of getting relevant and up to date information sent to you for you to read in your own time. It saves you time and helps you to get the information you want quickly after it was published. I find the ‘subscription’ description helpful. It’s like subscribing to a magazine that is delivered to you periodically but instead of it coming in your physical mail box each month when the magazine is published it is delivered to your RSS Reader every time your favorite website updates.
The first thing you'll want to do (if you are not already reading sites via RSS) is to hook yourself up with an RSS Feed Reader. There are many feed readers going around with a variety of approaches and features, however a good place to start is with a free and easy web based one. This is a link to a recent article which should help you with more background and choosing a reader. As the article states: "There are apps for every reading style, budget, and platform..." I use Feedly and know that it is reliable and easy to use.