Fun fact for those who (like me) didn't know for a long time... technically "gmail.com." is actually the domain name for Gmail. It's called the fully qualified domain name (FQDN), akin to an absolute domain name (as opposed to relative to the current subnet).
As a German (we don't do this), I also didn't like that when I saw it the first time.
[1] http://www.thepunctuationguide.com/british-versus-american-s...
Actually it's right there in the Wikipedia article [1]...
The DNS root is unnamed, expressed as the empty label terminated by the dot. This is most notable in DNS zone files in which a fully qualified domain name must be specified with a trailing dot. For example, somehost.example.com. explicitly specifies an absolute domain name that ends with the empty top level domain label.
[1] https://en.wikipedia.org/wiki/Fully_qualified_domain_name#Sy...