There are many, surprisingly, who cannot differentiate between website and webpage with the result that they use the words interchangeably. This is incorrect as webpage is just a subset of website and a website may be anything from a single webpage to hundreds of webpages linked together through navigational links. A simple definition of a website is a collection of web pages.
When we talk of a website, we refer to a huge amount of information spread over many pages but when we talk of a web page we are referring to a screenshot which is a small subset of the website and can be used for a particular purpose. The differences between a web page and a website can be summarized under these criteria.
Size
Websites can range from the most simple, single page ones to huge websites that run into thousands o0f web pages. One example of a huge website is FaceBook where each member has a webpage on which he makes his profile and interacts with other members. Small businesses normally have small websites that run into several pages but a website can be a single webpage one also.
Content
The content of a website is varied with different webpages containing different information. Big companies may have a contact me page, signup page and so on. Content on a single webpage contains specific information only.
Creation
A website is created in much the same way as a webpage. After completing a webpage, navigational link is created to connect it to other pages of the website.
It is clear then that the best analogy that can be drawn with a webpage and a website is that of a page and a book.