Internet Cookies 

The definition
Cookies were created because websites weren't available to track who was visiting pages and it causes some troubles with user login system management.

A cookie is a text file that contains some text data. It is stored on your computer system, and is incapable of performing any tasks or functions by itself. Cookies are stored by a Web sites that were visited by user. It may contain some identifying information that was needed in the Web site or information about the visit.
Cookies are tied to a specific web address (for example a domain, a sub-domain , or even a folder ). Let's say you have visited some site. After some time you are visiting it again. And during the second visit your Internet browser checks if there are some valid cookies for that page. If cookies are valid, the information is sent back to the server. Information contains only that data that was given by server the first time. So to say in one sentence a HTTP cookie is a packet of information that is sent by a server to a Internet browser and then sent back by the browser each time it accesses that server.

If user has more than one browser and they are different, like Internet Explorer and Opera, each browser has a separate storage are for cookies.
Usage of cookies
Sometimes cookies are wrongly considered as spyware because they have the same function - they track user's information. Yes, that's right, cookies do track user's information from Web site. But this is only for good and legal purpose, for authentications and identification of registered user. For example to remember some actions that were made on the Web site or some information about user so that he didn't have to fill in that information every time he visits the site. Mots Web sites that provide shopping services use cookies to provide convenience.
It is also used in Internet advertising market. Cookies give some feedback for the site about user's opinion and expectations about advertising. It enables targeted advertising which is more effective and convenient for users and site's creators. Advertising companies like "DoubleClick" place data on web pages. It's mostly images, text links and banners. If the advertisement is from another server, unlike the rest web site, it might sent a cookie set. But it's normal for this market.
How can Cookies be Abused?
Although cookies were created for legal purposes and for convenient , there were some events where cookies were used as spyware. There times when cookies had to track information without users knowledge, while this is the function of spyware. This might be a great threat to user's privacy, but not for security.
Some sites contain images that are called web bugs. These bugs place cookies on all computers that access them. They are very small and transparent. Sites, that provide e-commerce services can read those cookies and using the information they sent advertising spam e-mails.
IT Managers also use cookies for their own purposes. With the help of cookies they get information about employee's surfing on Internet and other actions that they were doing at the workstation. Parent can track their children surfing habits and to find out either they were connected to sites that are for adults.
Cookies sometimes can contain private information. It's not very dangerous because cookies contain only that information that you give to the Web site and only that Web site can retrieve that information.

I don't want cookies

If you still think that cookies are harmful to your PC and your privacy, you can avoid the. Most of the Internet browsers provide cookies control function. You can decide either to accept or to reject cookies.