A new session is recorded when a visitor arrives on your site. As they view additional pages, these views are included in the same session until there is a 30-minute period of inactivity. If that visitor views any pages after that, they’ll be recorded in new sessions.
As an example, if a visitor arrives on your site, views 5 pages, and leaves, this will be recorded as 1 visitor, 5 views, and 1 session. If that same visitor returns the next day, views 2 pages, and leaves, the total values will be 1 visitor, 7 views, and 2 sessions.
Sessions are a valuable metric because they tell you how many times visitors used your website.