RSS

The RSS was a simplification. What I'm talking about are web/news feeder, and what they read are file formats that contain information about whatever link you put in them, like Neocities pages, Twitter Accounts, blogs, etc. So long as they're in a format it can read.
It was mostly used in the past, although nowadays people still use it but it's a niche.

The file formats it reads are: RSS/Atom/JSON/ links, along with a few others depending on the app, but those would be the main ones (no promises in how they look in the Web/News feeder itself when you preview it, that's up to the person who does the RSS, and if they stylize it.)

The way it works is simple. You can grab an application or addon that is a feeder and, just like a Twitter or Instagram feed, if you put links about what you want to be updated about you will be notified every time it updates. It depends on what app you use that you may be shown a live-preview aswell.

They look like this:

These are the platforms that appear in the images:
1. Selfoss
2. Feeder
3. Feeder (Google Addon)

Please note that I haven't used or checked any of them beyond surface-level to give credit.

I've also additionally found these things that maybe you'd like to use.

Apps:

Tiny Tiny RSS

It's a web reader, free and open source. It can only read RSS and ATOM. Can be self hosted for privacy.

Free, can use it as a browser extension for Firefox/Chrome or as a desktop app, and it's available on Linux, Mac OS X, and Windows. Uses RSS/Atom/JSON, although it can read a lot of things from what I've read in the website, check it out!

Can be downloaded in distro's stores (Linux) or in their Github. It can be web-synced, and has a lot of features. You can import/export feeds, and have backup/restore database settings.

Can be downloaded from their website (supports Linux, Windows and Mac OS) or in Linux's stores, if it doesn't exist from the get-go. It's actually for Gmail stuff but it has a RSS client, reads RSS/ATOM I believe.

Terminal based feed reader. It uses RSS/Atom formats to read. It doesn't have a lot of features. If you know how to install it and use it, go ahead! If not, wait just a little bit longer to get more experience.

And also, there's readers in Android! (Like the first screenshot of a RSS I used as an example) I just don't have enough energy right now to search and read through them though. Do your own homework!