what makes up a web page?
This is what appears along the top of people's browsers, telling them something about your page. Your organisation name, maybe a short strapline or brief content information, would go there. Forget it and you'll be viewed as Untitled Document and look very amateur!
The basic elements of a page are a banner, logo or some form of design that identifies the person or organisation behind it. The simplest example would be a logo or banner across the top.
Then there's the menu or navigation system, usually some form of buttons or links to get you from page to page (and hopefully back again!)
Next there's the text content. The stuff that people read.
Then there are the images, photos, graphics that illustrate the content. A site may not have to have images but without them you'll have to work much harder to make the page look attractive or easy to read.
Lastly, for most sites, there'll be an area where visitors can see some basic information like an address, designer info, contact information, when it was last updated or other (possibly, but not necessarily,) small print.
These comprise the page elements and how they are placed on a page is the page structure. Ideally, the structure should be consistent across sections of a web site, if not the whole site. There will, of course, always be exceptions and one example would be the home page of a site which can be different in that it may not need all the elements. Once inside, though, visitors can be confused by elements switching positions or even disappearing!