Here's how they work in a nutshell. Suppose Dr. Drang's blog and my blog both support webmentions and he links to a page on my blog (don't ask me why).
- His blog looks up the page that he linked to (joeldueck.com/posts/argyle-is-fun) and sees in the header of that page a
link tag with rel=webmention and href=joeldueck.com/mentions.php. So now his site knows where to send the mention.
- His blog software sends an HTTP request: to
joeldueck.com/mentions.php with source=leancrew.com/argyle and target=joeldueck.com/posts/argyle-is-fun.
- My site then checks his site to make sure it actually contains a link to joeldueck.com/posts/argyle-is-fun, and if it does, accepts the mention as "valid".
- Now that the mention is accepted, my site can (at my option) display the mention on my post, and/or notify me by email, or whatever.