Template:TB

Documentation
Use TB (talkback) when you want to notify someone that there's a reply to a talk page, for example - if you've replied to someone's message on your talk page. This helps keep the conversation in one place, whilst still allowing you to notify the user.

notifies a user that you've sent them a message, and gives a link back to your talkpage.

If you add a third argument, I.e. - then the template will say "at Bar's talkpage" and link to User talk:Foo