A single web page viewed by a human through a browser is a pageview. Technically: a file, or a combination of files, sent to a visitor as a result of that visitor's request being received by a server.
WAA Definition of pageviews: The number of times a page (an analyst-definable unit of content) was viewed.
For the day that you are looking at the Forecast report, you will see;
a) how many users/ visitors will visit your site by the end of today, and based on that:
b) how many visitors/ users and pageviews are predicted to occur on your...