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.