||What are cookies?
A "cookie" is a small piece of information sent by a web server to store on a web browser so it can later be read back from that browser. This is useful for having the browser remember some specific information.
What are they used for ?
Online Ordering Systems.
An online ordering system could be developed using cookies that would remember what a person wants to buy, this way if a person spends three hours ordering CDs at your site and suddenly has to get off the net they could quit the browser and return weeks or even years later and still have those items in their shopping basket.
This is one of the most beneficial uses, let's say a person comes to the MSNBC site but doesn't want to see any sports news. They allow people to select this as an option, from then on (until the cookie expires) they wouldn't see sports news. This is also usefull for start pages.
Here is a hot button! A lot of people think it is an invasion of privacy, if a web site designer wanted to see what interests them. Site tracking can show you "Dead End Paths", places in your website that people go to and then wander off because they don't have any more interesting links to hit. It can also give you more accurate counts of how many people have been to pages on your site. You could differentiate 50 unique people seeing your site from one person hitting the reload button 50 times.
In Internet Explorer the first part of the cookie is your windows log in name, It's not certain if this is passed on to the server.
How Do They Work
A command line in the HTML of a document tell the browser to set a cookie of a certain name or value. Here is an example of some script used to set a cookie.
Set-Cookie: NAME=VALUE; expir es=DATE; path=PATH; domain=DOMAIN_NAME; secure