RSS (really simple syndication) is a way to watch new articles, videos or podcasts from a variety of sources in one place. Any creator who wants to share their stuff in this way will create one single file with the so-called RSS feed in a simple format. Users then download the feed and use a simple program to translate it to learn what the news is.
To view news from RSS feeds, you need an app that reads RSS feeds. On PC, I recommend the command line newsboat application. The video that explains its workings is here. On Android/iOS, I recommend the open source application AntennaPod, which is primarily for podcasts, but you can also view articles through it, etc.
You must always add the url of your RSS feed to your RSS feed. My site is https://jidu.cz/RSS/RSS_jidu.xml, other sites mostly give their RSS feed address on the site.
It is even possible to receive information (for free) from RSS feeds to mail via the service blogtrottr. RSS feeds can also be created from YouTube channels and other social networks.
If you want to create your own RSS feed, there's nothing easier. Basically, it's about putting a file in .xml format somewhere in the public domain. You then regularly insert information about new updates into it, and users can see the changes through their RSS applications. Instructions for formatting feeds can be found here, indeed it's really simple.