(1) The session of activity that a user with a unique IP address spends on a Web site during a specified period of time. The number of user sessions on a site is used in measuring the amount of traffic a Web site gets. The site administrator determines what the time frame of a user session will be (e.g., 30 minutes). If the visitor comes back to the site within that time period, it is still considered one user session because any number of visits within that 30 minutes will only count as one session. If the visitor returns to the site after the allotted time period has expired, say an hour from the initial visit, then it is counted as a separate user session. Contrast with unique visitor, hit, click-through and page view, which are all other ways that site administrators measure the amount of traffic a Web site gets. (2) The period of time a user interfaces with an application. The user session begins when the user accesses the application and ends when the user quits the application.