Like everything on the traditional Web, each of the pages mentioned above are Web documents. Every Web document has its own URI. Note that a Web document is not the same as a file: a single Web document can be available in many different formats and languages, and a single file, for example a PHP script, may be responsible for generating a large number of Web documents with different URIs. A Web document is defined as something that has a URI and can return representations (responses in a format such as HTML or JPEG or RDF) of the identified resource in response to HTTP requests. In technical literature, such as Architecture of the World Wide Web, Volume One [AWWW], the term Information Resource is used instead of Web document.

[..]

According to W3C guidelines ([AWWW], section 2.2.), we have a Web document (there called information resource) if all its essential characteristics can be conveyed in a message. Examples are a Web page, an image or a product catalog.