Okay, I think most of us SharePoint "people" already know that a web application can be given a host header. A host header is a FQDN or Fully qualified domain name. If we are on good talking terms with our DNS experts we can get FQDN URLs like https://portal.company.intranet.com.
Okay, so what can we do with this?
One of the problems with developing Enterprise solutions is that you have clusters of experts who maybe speak to each other for an hour and pass paper work around. For a SharePoint person a FQDN is just something they need to make host headers work.
But to a DNS expert FQDN open the ability to strucutre a intranet space. The FQDN provides an "exact location in the tree hierarchy" of the DNS, which means that a large tree or cluster of names that will help the user understand the Intranet.
Let us say our company intranet has a domain name ourcompany.com. Using DNS FQDN we can define, in DNS, names like portal.ourcompany.com, hr.ourcompany.com, collaboration.ourcompany.com.
By planning this tree out with our DNS team as part of the Information Architecture of SharePoint we can make the structure of the intranet more logical and easier to use.