subscribe to comments
If you leave a comment on a post or page you will have the option to be notified via email of all future comments on that post/page.
subscribe to RSS/news feeds
If you want to subscribe to news feeds you'll need a feed reader. Some web browsers and email clients have one built-in, however it may be rather rudimentary. If you would rather use a web browser extension, check the extension repository for your browser. For Firefox it is addons.mozilla.org (you can find my preferred feed reader here). There are also many stand-alone feed readers for whatever operating system you're using, whether it be Android, iOS, Linux, Mac, etc..