A HostID is a unique machine value, which can be used to lock a license file to a specific host. 

LM-X provides a great deal of flexibility to give you fine-grained control over your licensing policy. For example, a license might be:

• Locked against a particular license server host (or license server hosts), so any client machine can use your application when using a license from the specified license server host(s).
  
• Locked against a client machine (or machines), so your application will run successfully if it is running on the particular machine(s) for which the license has been granted.
  
• Locked against both license server host(s) and client machine(s), so your application will run successfully if it is using a license from the specified license server host(s) and is running on the particular machine(s) for which the license has been granted.
  
• Using HostID match rate, a license may be locked to multiple HostID values but allow users to run the software if a specified percentage of the HostID values are valid. See  HOSTID_MATCH_RATE for more information.

Note: For performance reasons, locking network licenses to the client's HostID(s) is disabled by default. To lock licenses to HostIDs, you must enable LMX_OPT_CLIENT_HOSTIDS_TO_SERVER.