Basically, it lets you specify a link that will position a web page at a string that you choose.
Here's a screen shot that doesn't use it.
Here's a screen shot that scrolls to "Beat".
Notice that the requested string is highlighted.
Now for the bad news. It's really hard to use.
Here's the URL that I used in the above example.
And I can't find a tool that lets you easily construct that URL. I use Notepad.
How-To Geek has an article on it.