RSS is a core feature of most content management systems like WordPress (which powers around half of all the web pages on the whole Internet) and many others besides. Most content sites, especially news sites, blogs, discussion forum software, etc. offer RSS by default unless they’ve disabled it for some reason. One the web, you can often just append /feed after the top level domain (like yourdomain.com/feed) but the easiest way is from within your RSS reader of choice. I like Inoreader and it has great tools for searching for feeds and subscribing.