[thelist] sub-domain???

[Bob Meetin]

I have never set up a sub-domain, am not familiar with the 
benefits/purpose.  However here is the situation... I have a site that 
is doing well on its own, but we are in the process of designing a child 
site (more tailored to a teen, young adult's audience).  In developing 
it I have it set up as a subdirectory of the parent, i.e.:

parent
parent/teens

Nothing complicated.  I have a number of SQL queries that are shared by 
the 2 sites, slightly different flavor.  I also have a custom stats 
script that without pain can separate out numbers fairly easily. 

Is this a candidate for a sub-domain or is that a different beast?  
Otherwise it would be easy enough to set up a new domain.

-Bob