Webmention is a simple way to automatically notify any URL when you link to it on your site. From the receivers perpective, it's a way to request notification when other sites link to it.
It’s a modern alternative to Pingback and other forms of Linkback. Webmentions are part of the IndieWeb movement.
This add-on allow you to send webmention simply by right-clicking a link while viewing a page. It allows you to send webmentions manually in a very simple and intuitive way!