RSS stands for Really Simple Syndication. It is a way of distributing content or updates through a news aggregator. If your visitors are using a news aggregator and would like to know the updates on your website, they can subscribe to your updates by clicking on the RSS feed button.
To enable the RSS Feed feature on your site, you can go to Settings > Social Media > find the RSS section > turn the switch to ON. The RSS Feed button will be displayed on your website along with your other social media buttons.