A host in Lab Management can be an Infrastructure node or a Client node.
Infrastructure nodes are those nodes that Lab Management uses to run itself. The Infrastructure nodes serve to maintain the Lab Management domain. The Lab Management Administrators are the only ones who can access the Infrastructure nodes and do so through the console or through shell accounts. The regular users (developers, for example) do not log in to the Infrastructure nodes directly except for the Lab Management Manager.
Physical Client nodes are physical machines, which can host virtual machines. Physical machines cannot be migrated to other physical machines.
Virtual Client nodes are virtual machines, which cannot host other virtual machines. Virtual machines can be migrated from one physical machine to another through the Lab Management Web Console.