In broad terms, a pageview is every instance that a particular page on a website has been loaded, or reloaded.
In slightly more complex terms, it is the number of times a ‘page’ file is requested. As such, individual viewers or users can generate multiple pageviews, as they move around a site or reload pages.
Pageviews do offer an idea of how popular individual web pages are, but the metric does need to be viewed in partnership with other analytics. For example, high pageviews from individual visitors or returning visitors might indicate that people struggle to find what they are looking for immediately.