Approval request notification

Hi all

I would like to know more about how email notification work and who is 
the recipient of e-mails being sent when a writer asks for the approval 
of page changes by using the built-in workflow.

Where is this documented ?
Could some one summarize it ?

For example I would like the members of a given group to be notified of 
the approuval request.

Additionnnally, is it possible to customize the message being sent ?

Thanks for your support,

Regards