RSS stands for Rich Site Summary, and is a method by which one can subscribe to frequently updated information online, much like how one might receive the text of a blog post in an email that is automatically sent when the blog is updated. There is an widget in Wordpress which allows people to easily subscribe to the content of your site through RSS.

First, hover your cursor over "Appearance" on the Wordpress dashboard, then click "Widgets" on the flyout menu. Drag the box labeled "RSS" to the "Sidebar: Left" section as shown below.