Some parameters are random ids, timestamps, others are about referrer, screen resolution, etc. One easy way to get more details about this is to install Firebug Firefox plugin. Activate the plugin then load a page with Analytics code on it and look for GET requests. You will notice one which goes to www.google-analytics.com. This one is the key and this sends all the information.
Note: You can use the urldecode() function on the GET request to make it easier to read.