Web page means one single page, one "screen" viewable in a browser. The web page could be a HTML page or a PHP page or an ASP page, but it's still just one page. These different file extensions indicate how the page is coded. And even on what kind of server it resides. Many people use the term and mean "website". There's hardly a website that has only one single page. But in creating a website we do it with a series of web pages somewhat similar as a magazine consists of many pages.