When your site’s metrics are Certified on Alexa you are given access to directly measured visits, pageviews, and unique visitors for your site.
“Unique Visitors” are the number of people that visited your site over the selected time period. A person visiting the site multiple times during the time period is only counted once.
A “Pageview” is recorded whenever a full page of your website is viewed or refreshed. The count of pageviews is the total number of times the pages of your website were viewed or refreshed within the selected time period. Pageviews are not uniqued.
A “Visit” is a single browsing session. If a visitor views another page on your site within 30 minutes of the last pageview it is counted as the same visit. If a visitor returns to your site after 30 minutes have passed since the last pageview then it is counted as a separate visit.