An RSS Reader is a tool that allows users to subscribe to and aggregate content from various websites in one place. RSS stands for Really Simple Syndication, which enables users to receive updates from their favorite blogs, news sites, and other online content without having to visit each site individually. When a website publishes new content, the RSS feed sends a notification to the reader, displaying the latest articles or posts. Popular RSS Readers include Feedly, Inoreader, and The Old Reader, which help users stay organized and informed about topics of interest efficiently.