P-Unlimited is the perpetual license level allows to run Cloud Hosted Router (CHR) indefinitely. It is highest tier license and it has no limitations enforced.
Perpetual is a lifetime license (buy once, use forever). It is possible to transfer a perpetual license to another CHR instance.
Cloud Hosted Router (CHR) is a RouterOS version meant for running as a virtual machine. It supports x86 64-bit architecture and can be used on most of popular hypervisors such as VMWare, Hyper-V, VirtualBox, KVM and others. CHR has full RouterOS features enabled by default but has a different licensing model than other RouterOS versions.