RSS Club is a collection of blogs (personal and otherwise) committed to providing RSS-only content. It’s like a newsletter delivered to your feed reader in order to celebrate the medium of RSS and breakaway from social media.
A feed is also known as a “web feed” and the technical term (which you’ll see a lot) is “RSS feed.” A feed contains the latest content in a form that your newsreader app understands. (Your newsreader checks the feed automatically, every few hours.)