The arrangement of pieces of content following one after another in time. Free from anyone's selection and care but the reader's. Unaltered by social media circuit breakers. Straight from the source.
RSS is a means of allowing basically anything online to be collated into a single feed. It puts the reader behind the wheel, and removes any form of intermediation between the source of content and the consumer of it. You follow, like in Twitter, but they don't really know; you like with the "Add to Feed" button, and dislike with "Delete". You are not in a platform, but on a protocol. The difference is subtle, but substantial.
On Facebook is a Doomsday Machine, author Adrienne LaFrance said that "We need people who dismantle [the notion that social platforms are free in exchange for a feast of user data] by building alternatives." Apparently, there's a good alternative already, one that had its heyday in the beginning of the twenty-first century, when the zeitgeist online was "do whatever you want with the information present". Before social media as we know it today. Before they siloed us off into their walled gardens.
The whole point of social media is monetization of awareness, and RSS offers none of it. It was disintermediated by design, protecting us from virality and addiction. Like email, it's a protocol, and not a platform. To have only what I want to see, shown only when I want to see it.
Its popularity peaked long ago, but RSS is still very much alive at Feedly, Newsboat or Fraidycat (the one I use). If you feel like trying out RSS for yourself, why not get started by adding this blog to your reader?