That isn't quite accurate.. It paints the wrong picture about localhost.
localhost is special, it's a special name that should always point to yourself. There is an entry about it .. and don't change that. If you do, a lot of things will start to break. localhost is called a loopback adress. It loops back to your computer, so.. localhost:80, points to the HTTP port on your computer.
A "local host name" is completely different from localhost. The local host name is the name of your computer. That's preety much it
The thing where it says <localhostname@something> Means.. <my computer's name @ my domain's name>
Just wanted to clear that up
, and to warn.. breaking localhost is very very bad. I don't even think X will start up...