What are Web Feeds?
Web feeds, also known as RSS feeds, are a way for websites to publish content so users can follow the site using the application of their choosing.
What is a Reader?
A reader enables users to subscribe to feeds so they can view content from several websites in one spot. Readers come in all shapes and sizes with different features for different audiences. Some look similar to email apps. Others, like Den, are designed to show a lot at once with dashboard-like organization. Some are made to fit feeds into your system toolbar. Some project feeds on your desktop. Some are built into web browsers either directly or through a browser add-on. Finally, there are many web applications for following feeds.
The most popular format for web feeds is RSS, short for Really Simple Syndication. Given its popularity, the acronym is often used when referring to internet syndication or web feeds in general.
Atom is another syndication format that includes specifications for more advanced interactions with feeds.
Both RSS and Atom feeds are based on XML (eXtensible Markup Language) and are interoperable in many ways. For example, it's common to find the Media RSS Specification used in both RSS and Atom feeds.
Den is compatible with RSS, Atom, and JSON Feed. All provide virtually the same content and user experience. Some websites will offer a choice between formats. In those cases, choosing Atom or JSON may provide some small performance benefit over RSS.