The Hosts console provides a hierarchical view of all currently defined hosts. Each host machine on which you have installed managers and agents must be added to the Framework Manager console through the Hosts console. Hosts are identified to the Framework Manager console by a unique agent name that is used during the registration process after installation.
Hosts are added to domains, which allow you to organize your hosts into a tree structure.The hierarchical structure allows for easy access to a particular host regardless of the number of Privileged User Manager hosts you have.
Section 3.6, Increasing the Security When Accessing the Framework Manager Console