Unique Visitors only count a person once no matter how many times they visit a site in a given month. A person can make multiple visits to the site in a given month.

Historically, site engagement was measured exclusively by page views; however, with the introduction of new technologies, such as AJAX and online video, sites are able to reduce the number of clicks a visitor needs to make to obtain the information they are seeking.

Since Visits Per Person is not dependent on Page Views, it is a great way to assess how effective a site is in retaining its visitors.