Number of unique visitors for the selected period. Visitor is a unique "Cookie", which is assigned to every user. If a user disabled cookies in the browsers a visit will not be counted.
Affinity Index
Affinity Index compares a share of objects in site audience to the share of objects in total audience.
Page views
The number of times a page was viewed.
Page depth
Total page views per visitor for the selected period.
Notes
Devices with high display density have more than one real pixel per one CSS-pixel of the page. This can be result of using special displays (Apple® Retina™, High Density Display Android) or using zoom setting in the browser.