Описание тега httpsession
An Java interface used by the servlet container to create a session between an HTTP client and an HTTP server. The session object has an expiration time which allows the container to invalidate the session after that specified time of the user inactivity. It is active while the user making requests, across more than one connection or page and remains active after the user exit application and stay active until it's expired. The server persists the session object for the user between restarts. While it's valid the session interface allows the application to bind objects to it and access then from different requests of the same user. A session usually corresponds to one user, who may visit a site many times. The server can maintain a session in many ways such as using cookies or rewriting URLs.