The license of this software is domain based i.e. it will only work on a valid domain name or website address that resolves over internet or intranet. When you get the license it will not work on IP address or local host.
A valid domain is nothing but a Fully Qualified Domain Name (FQDN) or complete domain name for a specific computer, or host, on the Internet. For example the valid domain can be yourcompany.com or support.yourcompany.com.
The domain field in this section indicates the license domain you have registered while ordering the license. There is certain restriction they are, If you ordered license with domain name www.yourcompany.com you will be able to install license on www.yourcompany.com/anyfolder, but you will not be able to install license on support.yourcompany.com (because sub domain is treated as separate domain)
Note: The main domain cannot be deleted or disabled. And when you delete the add-on domains then it will delete all the departments, tickets and clients under that domain.
With Satellite helpdesk and Service desk you can add multiple domains and multiple customer portals. Help desk license have single domain the one which is registered with the product.