Cookies are small piece of data that are stored on client’s browser. These are send with the request to the server and the server also sends back the cookies.
Cookies helps us to store the necessary information on the client side. Later we can use this information for session management, for personalized recommendations.
Cookies also helps the server to recognize the user back, if he accesses the website after some time. In this way the user doesn’t have to provide the details each time.
Confidential informations must not be stored in cookies, as it can be easily accessed by anyone, through internet or the web browser itself.