Webmention is the more modern specification now as some have mentioned. I wrote a piece on it in @alistapart recently which includes some background, UI examples, and links to more technical resources:
It is a small part of an #IndieWeb suite of open protocols including Micropub, WebSub, and Microsub for allowing site to site communication and interaction which goes to the broader scope of your question about RSS feeds and blogs. See also: Lost Infrastructure
I keep meaning to provide a better overview of it all, but this recent pencast overview captures a chunk of it. Aaron Parecki’s article Building an IndieWeb Reader captures some of the rest of the microsub/reader portion.