When you link to a website you can send it a Webmention to notify it and then that website may display your post as a comment, like, or other response, and presto, you’re having a conversation from one site to another!
A Webmention is a notification that one URL links to another. Sending a Webmention is not limited to blog posts, and can be used for additional kinds of content and responses as well.
For example, a response can be an RSVP to an event, an indication that someone "likes" another post, a "bookmark" of another post, and many others. Webmention enables these interactions to happen across different websites, enabling a distributed social web.
The Webmention plugin supports the Webmention protocol, giving you support for sending and receiving Webmentions. It offers a simple built in presentation.