A site map expresses the structure of a site.

It might not show every single page, or all the links, but it shows the main buckets or divisions of the web site and what you might find in each of those sections.

There are lots of different styles to sitemaps. The important thing is to be neat, clean, and make a document that can be understood or explained to others.

Here are some examples of site maps that I have made in the past.

Click on the maps to embiggen

   

Here are some sitemaps I found online