The #lt;map#gt; element has existed in HTML since earlier than version 2 of that specification, about 1996.  The facility it invokes is known as "client side image maps".  (There also exist "server side image maps" that predate this facility, but they are so primitive as to not be very relevant to the discussion of modern Web maps).<br/>In native "client side image maps", the #lt;map#gt; element can be associated to an #lt;img usemap="..."#gt; element, via the latter's "usemap" property, which must reference a #lt;map name=".."#gt; by its "name" attribute value.  <br/>Since some browsers allow Web dev to use a spec called "Customized built-in elements", to enable custom behaviour on existing elements, we created a custom built in #lt;map#gt; element implementation of the map viewer package, and it is implemented by the WebMap class, using the customized built-in facility of certain Web browsers.<br/>The purpose of this implementation was to demonstrate that a new map viewer could be introduced to the Web platform and it could have a "fallback" / progressive enhancement story.  In the age of evergreen browsers and specs evolving together, this is a less compelling motivation, but we've (tried to) maintain it nonetheless, as the tag name "#lt;map#gt;" makes quite a bit of sense for a new HTML user and it might be a (bad) surprise that it doesn't implement Web maps, or that there are two different kinds of map that don't share conceptual parentage.<br/>