The term Cookie
derives from "magic cookie", a packet of data a program receives but only uses for sending it again, possibly to its origin, unchanged. Magic cookies were already used in computing when Lou Montulli had the idea of using them in Web communications in Mar 1993.
HTTP cookies are used by Web servers to differentiate users and to maintain data related to the user during navigation, possibly across multiple visits. HTTP cookies were introduced to provide a way for realizing a "shopping cart" (or "shopping basket"), a virtual device into which the user can "place" items to purchase, so that users can navigate a site where items are shown, adding or removing items from the shopping basket at any time.
Cookies are also used to track users across a website. Third-party cookies and Web bugs, explained below, also allow for tracking across multiple sites. Tracking within a site is typically done with the aim of producing usage statistics, while tracking across sites is typically used by advertising companies to produce anonymous user profiles, which are then used to target advertising (deciding which advertising image to show) based on the user profile.
Described in " How to Enable Cookie " section.
Persistent cookies have been criticized by privacy experts for not being set to expire soon enough, and thereby allowing some websites to track users and build up a profile of them over time. This aspect of cookies also compounds the issue of session hijacking, because a stolen persistent cookie can potentially be used to impersonate a user for a considerable period of time.
If more than one browser is used on a computer, each usually has a separate storage area for cookies. Hence cookies do not identify a person, but a combination of a user account, a computer, and a Web browser. Thus, anyone who uses multiple accounts, computers, or browsers has multiple sets of cookies.
Likewise, cookies do not differentiate between multiple users who share a computer and browser, if they do not use different user accounts.
*** The above information is for reference only, Please seek independent technical advice if found necessary.