People keep asking me this, or asking this within earshot of me. Here's my post about it. Other people have better posts about this stuff but I'm making this one for my own sharing use.
RSS means "Really Simple Syndication". Syndication in this context, means presenting information in a standard form for other things to ingest it. To be more specific, it means a website presenting Things in a standard form, so an RSS Reader can read them. If lots of websites are all presenting information the same way, this means that your RSS reader can show you say, all the latest news posts, blog posts, webcomics, masto/bsky posts, and even youtube videos, all in a single place. And you have control over how that's presented.
Technically, an RSS feed is just a link on a website. It's XML, which is like HTML but it's not. Basically, it's just fancy text. There's no magic protocol or API or whatever, it's Really Simple after all.
RSS feeds have been around for a long time, the RSS icon itself (this orange thing you're seeing) turns 20 years old this month on the 26th. You've probably seen it around, because it was very popular 10-20 years ago, and lots of people still use it. The upside of this, is that a lot of websites have RSS. Way more than you would expect. I personally glossed over those orange icons for many many years. I was a fool.
RSS readers also give you control over how that information is presented to you. A website can still choose how much information to present, say a news site only giving you a headline and one paragraph and asking you to visit the website to read the whole article, but if a site does give you a whole post, you can say, choose what font you want it in. Decide if you want images or not. Etc. Personally I use RSS to just tell me about things, which I go and open in a web browser, but some readers are very good at letting you not need to leave the reader often, if at all.
Also, RSS readers can be local, as in they just run as a program on your own computer, or on a server somewhere (your server, someone else's, etc) so that you can check it from different devices, i.e. your desktop and your phone.
A particularly well made blog or website won't just have an RSS feed for the whole blog, but also create feeds for any given tag used on it. You may think "oh but if I want to follow more than one tag, it's going to create a ton of duplicate entries in my reader" but most readers are smart enough to dedup for this exact reason.
The last very important thing to know, is that all RSS readers can export data in a standard format, OPML. This means that if you add a ton of websites to an RSS reader, but find a different reader that you decide you like more, you can just export all of those feeds, the layout of them, folders, etc, to a single file and import them into any other RSS reader. There's no lock in, RSS existed before everyone wanted lock in.
More resources:
https://candiedreptile.club/bloglet/posts/2024-09-10-RSS-Resources.html from cohost user @zygodactyl
Consider the fact that, even if you want to limit yourself to major "microblogging platforms", both mastodon and bsky support RSS with zero extra work on your part.
Twitter does not, and due to all of their API lockdowns, a service can not exist to create RSS feeds from them.
If you only post on Twitter you are massively limiting your audience.
And most of that audience now are racists, cryptobros, bots, and just other people that you don't actually want to do business with anyway. Stop it.
