The page() function

I found many files have the function page() in the class.

But I can't find that where the function executed?

There is no page class, it is simply set per controller.

There is a setting for the page drop down:

$view->set('action', $url->ssl('category', 'page', array('path' => $request->gethtml('path'))));

that is where the page drop down is triggered to call the page() function in that page

Ok, I understand now.