Newbie question: exposing a "sub" domain

[Beau E. Cox]

Hi -

I have bind 9 up and running on my Linux server.

I have a registered domain, say "mydomain.com".

Can I expose "someplace.mydomain.com" to the
external world, or do I have to register my
nameserver or "someplace.mydomain.com"?

In a nutshell:

If a public nameserver out there in i-land gets
a request to go to "somplace.mydomain.com", does it:

1> look up "someplace.mydomain.com"
2> It will not be found.
3> then, lookup "mydomain.com" -or- fail?

Sorry I seem to be clueless (I am!)

Aloha => Beau.