See below for an explanation of how networks are set up. A "Network" account adds one additional level to the usual setup of display groups within an account - Network users are at the highest level, and can add accounts within the network, in addition to Display Groups within the accounts.
Note: There is no concept of a "limited network" user. By definition, network users have full access to everything within the network.
Normal account users (both limited and admin) can only see what is within their account - they cannot access other accounts.
Admin users can see everything within an account, while Limited users can only see the display groups they have been given access to. See below for more details: