A pageview is an instance of a page being loaded or reloaded in the browser. Repeated views of a single page are also counted.
However, Pageviews is a browser metric, which does not in any way describe the nature of the connection site visitors had with the content.
We could say that the more precise name for Pageviews would be Page Openers or Page Loads, since this metric does not necessarily show the number of people who viewed the page (let alone read it), but only the number of times the page was loaded in the browser.
Article Reads in Content Insights is a metric that counts the number of times a person has opened the article, spent at least 10 seconds on it, and started consuming content.
Unlike Pageviews, Article Reads focuses on real human behavior, as it takes into account the way people interact with the page (e.g. clicks, text selection, scrolls, etc.).
1 Article Read = somebody opened a page, spent at least 10 seconds on it, the page was in focus and there was an actual human being behind the screen.
We know that there is human behind the screen because we don't fire this event unless there is some kind of activity on the page - mouse moves, scroll, click, selects, etc.