Web Page
Also known as: Page
A web page is one page of a website, the same way one page of a coloring book is part of the whole book.
A coloring book is not one page. It is lots of pages, held together, and you can open it to any one of them.
A website works the same way. The whole website is the book. Each page inside it is about one thing. One page might be about lemonade. Another page might be about where your stand is. Another page might be about how much a cup costs.
Color this: draw three pages for your own book. Give each one a title. Only one thing on each page.
For the grown-up holding the crayon box:
One page, one purpose is the rule that keeps a site useful for both people and search engines. A page trying to be about four things ranks for none of them and confuses the reader, which is the same failure in two different vocabularies.