A host is a system with a TCP/IP address. There should be one HostName entry for each host on which you have installed Blueworx Voice Response Java and VoiceXML Environment.
Every time you install Blueworx Voice Response Java and VoiceXML Environment on a host, a configuration file is created, including an entry for HostName=LocalHost. However, when you start adding hosts together to create a plex, you need to create a HostName entry for each host in one single configuration file: see Managing a network of nodes. Warning: Make sure that no applications are running before you change the TCP/IP address of a host.