cookie

Cookie, sometimes using the plural form of Cookies, that certain websites in order to identify the user, the session tracking and stored in the user's local terminal data (usually encrypted). Defined in RFC2109 (obsolete), the latest specification is replaced by RFC2965.
Initiated
Cookie was originally a former employee of Lou Montulli Netscape in March 1993 of the invention.
Cookie is generated by the server, sent to the User-Agent (typically a browser), the browser will be Cookie's key / value saved to a text file in a directory, the next request to send the same site to Cookie server (provided your browser settings to enable cookie). Cookie name and value can be defined by the server-side to develop their own, for the JSP can also be written in terms jsessionid, so that the server can know whether the user is the legitimate user and the need to re-login and so on.
Use
Cookies contain information the server can be used to filter any of the information, and regular maintenance in order to determine the status of the HTTP transmission. Cookies The most typical application is to determine whether registered users visit the website, the user may be prompted to enter this web site is the next to retain user information in order to simplify registration procedures, which are the function of Cookies. Another important applications is the "shopping cart" like handling. Users may within a period of time with different pages in a site choose a different product, the information is written to the Cookies, the final payment in order to extract information.