a variable that remains in a Web server's memory throughout the time a user visits your Web site

a variable the persists from one page to another without physically passing that information

Session variables are pieces of information stored in the session (see session). Session variables make that information available to all of the application's pages for the duration of the user's visit. For instance, the username can be stored as a session variable.

A variable that is associated with a user session. The user can change session variable values for each login session. Session variable values can also be securely saved for reuse in subsequent sessions.