Each HTML document that is delivered by wao.io counts as a Delivered Page. Each Delivered Page rendered in the browser counts as a Page View (also called Page Impression).
A real user creates a Page View while a bot generates a Delivered Page by crawling your site.
Only HTML documents with HTTP status code 200 are eligible as Delivered Pages. If, for example, a missing icon generates a 404 error page, that is not a Delivered Page. HTML fragments, that are often requested via XHR, do not count either.