How link to internal sections of a page (document fragment) with anchor elements can be achieved?

<!-- This is the link to the fragment -->
<a href="#contacts-header">Contacts</a>
...
<!-- This is the fragment identifier -->
<h2 id="contacts-header">Contacts</h2>

The octothorpe symbol (#) (also called hash, pound, or number symbol) indicates the link is to a fragment and not to a file.

<!-- We can also link to a section of a page located in another site -->
<a href="https://www.anothersite.com/index.html#contacts-header">Contacts</a>