What does the 'domains license' mean?

Once you choose a membership package you get access to all premium products and a specific number of licenses. These are limited by the number of domains/sites you can use them on at a time. 

For every site/domain the license is activated on, it reduces your total number of licenses for that specific theme/plugin by 1. Subdomains are also considered as unique websites, so activating a license on https://example.com and https://website2.example.com would use 2 licenses from your total license count.

We hope this clears things up. If you still require assistance then submit a presales ticket here and we'll be happy to assist: https://themeisle.com/contact/