An HTTP Cookie (also known as a web cookie or browser cookie) is a small piece of information stored by the server in the user's browser. The server sets the cookies while returning the response for a request made by the browser. The browser stores the cookies and sends them back with the next request to the same server. Cookies are generally used for session management, user-tracking, and to store user preferences.
Cookies help server remember the client across multiple requests. Without cookies, the server would treat every request as a new client.