Cookies are small text based data files containing information which are saved on the visitors computer. When you visit the website the files are sent along, allowing the server to keep track of the users preferences or identity (to the extent the latter is known). The purpose of using cookies is to make the the user experience as smooth as possible by allowing users to stay logged in, remembering the users preferred language settings on the website, gathering information on the way users interact with the content or presenting the user with advertisements based on their previous searches and purchases.
Cookies can contain information in clear text but are often encrypted. It’s common that the cookie only contain a key to a data base-post on the server, while the user can’t control the amount of information stored about him/her.
The cookies contain information about a specific point in time after which it can no longer be used. Cookies who are only valid during the time the user have the same browser window open are called session cookies. There are also cookies that are permanently stored on the users computer to save information such as preferred language, login and similar information.