Determining Unique PageViews for once and for all


#1

I would like t have a full definition of what constitutes a Unique PageView and/or how to tell from my piwik settings (I didn’t install my instance).
So what I get from reading the forums and faqs is: every time a unique visitor hits a new page this is considered a unique pageview and him returning to that page constitutes a regular pageview.
Now, how are unique visitors considered so as to account for unique pageviews? If a person returns the next day to my site, will they be considered a new visitor and account for a unique pageview for that day? Will they be returning visitors but also account for a unique pageview or for just a pageview?
So my question can be boiled down to the time between vistis that a person could be considered a new visitor and account for a unique pageview.