One of the most popular questions I get asked is to explain what is the difference between users (formally unique visitors), sessions (formally visits) and pageviews.
Best way to do this is with an example (see below)
To quote Justin Cutroni
“Digital analytics data is organized into a hierarchy of hits (pageviews or event views), sessions and users”
So users will have the least numbers, sessions will have more and pageviews even more.
What people also need to understand is that all metrics inside GA are split into two camps. Session Metrics and Hit Metrics. Sessions are to do with the session overall so think sources, time on site, goal conversions. Hits revolves around what is tracked during a session, so think pageview, interactions (download click, video play click, carousel click) time on page.
You should never mix the 2 types up either as they are separate, for example looking at top pages you only get pageviews, you can’t get sessions or users.
To quote Avinash Kaushik
“Hits are from Venus and Sessions are from Mars”
The Example (with help from Kylie and Jason)
As you can see the example contains 2 users with 3 sessions (simple enough)
Looking at each user you can see pageviews and unique pageviews (again pretty simple). The difference is that unique only records once no matter how many times its viewed. Also note in many cases interaction on a carousel, an expandable, a video etc will also trigger an additional pageview.
Things get interesting when adding these figures up, especially unique pageviews. Now as mentioned before users and unique pageviews are from separate groups of metrics so are independent of each other. When Google calculates total unique pageviews it doesn’t see them coming from different users, but just as a whole, hence in the example we have just 6 unique pageviews for 3 pages (homepage, page 1 and page 2).