Thomas Williams passes along querystring data:
As background, a query string is part of a web page address. Query strings are used to pass information to web pages, in name/value pairs separated by an equals sign – for instance,
user=Andreworcountry=au. Name/value pairs are themselves separated by ampersands, so passing multiple values looks likeuser=Andrew&country=au.
Click through for an example of how it all works.