You cannot change the string in the url bar to a random text. The address bar will always contain an url, and that url will always begin with your domain.
If a browser would opt to display a text in the url bar instead of the actual url, it would be the title you set for your page. This happens in the <title>
tag in the <head>
of your html document.
You can change the displayed url through the window.history
api of javascript, but this will only allow you to change the url to one that is relative to your domain. See this question for more information.
This question will give a general overview of the functionality of mod_rewrite, a module for Apache, that you can use to translate url requests to a specific file on your server. You can also make the browser do a redirect, but you will not get anything sensible out of it when the redirect isn't to an url.