The type of license for Red Hat Enterprise Linux depends on the type of processor and the environment in which they will operate.
Purchases of Red Hat Enterprise Linux products are made on a physical or virtual basis. If you are deploying Red Hat Enterprise Linux on physical hardware, your subscriptions are based on the number of socket-pairs in the systems used. This model is best for provisioning to physical hardware or as virtual instances in the cloud. If you are deploying Red Hat Enterprise Linux in a virtual environment, your subscriptions are based on the number of virtual instance-pairs running the product. This model is best for low- and medium-density virtual environments.
Red Hat also offers a subscription model that allows you to run an unlimited number of Red Hat Enterprise Linux virtual instances and is best for high-density virtual environments. This subscription model is offered on a physical socket-pair basis.
More information on the website Red Hat.