The road not yet taken on the Web. There is no converse way to find pages which have links pointing to the current page.
Forward links are so handy that backward links are often forgotten.
Anyone who is linking to your site must think you are interesting in some way, either good or bad. If you've got something to say about someone else's site, whether it be a sales brochure, political platform, or research paper, you can link to it from your comment. It doesn't do much good, though, as no one on that site can find that link. Backward links would allow others to hear you say your piece. There are a few ways to do backward linking.