apex domain

 apex domain  is a jargon term for a plain domain name, like just the domain name, the way the vast majority of sites, companies, and IndieWeb folks present their websites & identities, right there at their domain, like indieweb.org, microformats.org, archive.org, or sf.gov, sfist.com, or even twitter.com & flickr.com, without a superfluous “www.” or other prefix.