What is RSS?
RSS is an old method of getting updates from people and projects you want to follow without giving out your email address or contact info to anybody, and it is still widely supported! Websites that support RSS will have a link to download an RSS file, mine is over to the left on the sidebar, the link called "rss feed". All you need to do is download an app on your phone like Feeder and follow the steps to copy the link into the app and you can get notified whenever I update this site!
How does it work?
The rss link there points to a file that I have on my server, and that file has every update I've ever made to this website with the timestamp and description for that update and everything. When your RSS aggregator starts following a new feed, it downloads that file and sees what the most recent update was, and then occasionally checks that website to see if there are any new updates. If there is a new update, your aggregator will just download that file again and display all the information for that new update and notify you if you have notifications set up!