Account_location couple of questions

Hi I’m having a look at the account_location plugin for a project and
there’s a couple of things i’m not sure on.

One is what the default_account_subdomain method does.

def default_account_subdomain
@account.username if @account && @account.respond_to?(:username)

What is this used for? Can anyone provide an example of it’s usage

Also, the authenticate method in the example controller, What exactly
this doing? This is essetially the same as the authenticated? method.
Again, what does it do, and how would i use it.

def authenticate
session[account_domain] = :authenticated
redirect_to :controller => “weblog”

def authenticated?
session[account_domain] == :authenticated

I would like to use this on an account level, but also have the standard
user stuff from acts_as_authenticated for individuals.
Any light on the subject is greatly appreicated.