How the google backlink checker tool work?

I know that the tool works like executing a "Link:www.yourdomain.com" search in google. But I want to know how the tool does this, I mean what they put in the form script?

<form action="what's put here" metho="post">
......
</form>

Thanks!

 

here's an example of goole code:

http://www.roscripts.com/PHP_display_keyword_position-134.html

 

I was going to ask the same question. Glad i found the answer