RSS stands for Really Simple Syndication. It is a mean of transmitting and updating news in an automated way.
To take advantage of an RSS feed you would use a piece of software called an RSS aggregator. Most of them are very similar to email client programs, but instead of incoming emails, they display news from various sources (from all the feeds you have registered with, or "subscribed to" as is commonly said but it has nothing to do with money). Unread news typically appear in bold, just as unread emails do.