In a business/family, domains can exist in two places. Either in the business/family container account (e.g. the masteruser account for the business/family), or in an individual users accounts within the business (we call these "personal domains", and currently only professional/superior accounts can have personal domains).
The main difference between business/family domains and personal domains is two things:
- Control (e.g. who can add aliases/websites to a particular domain). For a business/family domain it's any administrator of the business/family (via Manage -> Domains/Websites), for a personal domain, it's the actual user that added the domain (via Options -> Domains/Websites)
- Creating accounts in that domain. (e.g. firstname.lastname@example.org vs email@example.com). Only domains in the business/family account can be used to create users at those domains
The general idea is that a user with the username firstname.lastname@example.org "owns" the domain space somename.example.com, and can thus setup their own website at http://username.example.com just by going to Files -> Websites in their account.
However if you want to setup a website http://www.example.com/username/, you'll have to do that through the business/family account via Manage -> Websites and using shared folders, because the business/family "owns" the domain example.com and (by default) the www.example.com sub-domain.
The bandwidth used by a website is counted towards whichever account the website is setup in. The business/family accounts have high bandwidth limits (the same as the top level business/family account), but low storage. This is because in general we thought it would be individuals storing files/photos, not the business/family as a concept, but realised that because of the domain issue, it might be common for websites to be setup in the business/family account via shared folders.