Atom and RSS are two different ways to provide syndicated content from a website. Although their formats vary, the way that they function is the same. And both RSS and Atom have two versions, variously known as RSS 1.0, RSS 2.0, Atom, and Atom 2.
RSS and Atom feeds use XML in order to distribute content from a WordPress or other type of website via a method that does not require visiting the website itself. RSS/Atom feeds can be read by software known as a feed reader or a news aggregator. Since RSS and Atom are the two most popular formats, most feed reader/news aggregator applications can handle either format.
The easiest way to think of an RSS/Atom feed is that it gives visitors a different way to access the content on your site other than having to visit your site with their browser. WordPress comes built-in with the automatic functionality of creating both RSS and Atom feeds from your website.
RSS was the original method to distribute syndicated content, but Atom was developed by some users who felt there were flaws in the original RSS format. It’s important to understand that the content doesn’t change between RSS and Atom, only the way it is formatted.
Atom is also known as the Atom Syndication Format. But Atom can also refer to the Atom Publishing Protocol or AtomPub, a tool that allows you to do more than just remotely access content from a site. AtomPub allows you to write, publish, edit, and delete posts, pages, and media files remotely as well. WordPress does not come with AtomPub but you can activate it with a plugin.