A cookie is a piece of text that a Web server can store on a user's hard disk. Cookies allow a Web site to store information on a user's machine and later retrieve it. The pieces of information are stored as name-value pairs.

Microsoft Internet Explorer (IE) stores cookies in different files on your hard disk drive. The more you browse the web, the more cookies are stored on your PC. Each cookie has its own lifetime - from several seconds to several years. However, IE does not remove expired cookies from your PC even if they are expired and will be never used. Therefore, your hard drive can store several hundreds or even thousands unused and useless files.