Invisible files in the URL

[blr32]

On a lot of big sites the name of the file seems to be hidden so that the url looks something like this

http://www.something.com/?kk=xx

how is this done - I suspect that it's something in Apache but what do I need to set up?

[eduard]

Simple, if you don't use a filename in your url, for example.. u have www.website.com.. When you type it in your laction bar, http://www.website.com appears. In fact now it opens a default file (such as index.php) now if you create a link in this index.php <a href="?action=logon">Log me on</a> for example.. the file index.php is opened. the only thing... index.php doesn't appear in de locationbar.