Session variables are designed to store session-level data. They are a convenient place to store information that all pages of your application might need during a user session, such as shopping cart contents or score counters.

Using session variables, an application can initialize itself with user-specific data the first time a user accesses one of the application's pages. This information can remain available while that user continues to use that application. For example, you can retrieve information about a specific user's preferences from a database once, the first time a user accesses any page of an application. This information remains available throughout that user's session, thereby avoiding the overhead of retrieving the preferences repeatedly.