What is an RSS reader? Before we can address that, I think we need to define RSS feeds first. RSS is an acronym for Really Simple Syndication. This is way to take the RSS specification that a site offers, and apply it to a specific program known as an RSS reader. When you click on the RSS feed link for Box News, it takes the news from that site, and brings it to your reader. Then you RSS subscribe to info from ESP Sports, and then you get updated sports scores as well. The RSS feed is what content a site puts out, to be viewed in your reader.
A RSS reader, the WordPress RSS plugin is just one example, is the one program that takes all of the feeds that you subscribe to, and keeps them all in order and up to date. It is like Microsoft Outlook or Mozilla Thunderbird. They keep track of all of your emails, from multiple sources, all in one easy to use, centralized location. This reader can cut down on time going from site to site to visit and read each one, in search of updates. It will do all of the dirty work for you and keep you up to date in real time.
As mentioned before, the WordPress RSS plugin is just one choice you have for a RSS reader. That reader is embedded right into your WordPress site. If you do not want to have to open an internet browser to get your RSS feeds, there plenty of independent programs available for download that will act as a separate entity, much like the Thunderbird reference I made. You can find dozens of apps available for your smartphone to stream these feeds as well. It will work much in the same way that a twitter smartphone app does, giving you headlines and links to the newest info from whatever sites you subscribed to, coming to you in chronological order.
RSS feeds are a super convenient way for you to stay on top of all of the sites that you check regularly without having to check each individual one. As they feed to you, you can get the whole story there, or even if you have to then go to the site to get the whole thing, at least you did not waste the time to go check on it every day. The only real problem with the RSS reader is that some sites do not offer an RSS feed for their content. Which makes the WordPress RSS plugin completely useless. But they do not deserve to have you read them anyway, do they?