What are instant clones (VMware) / pooled virtual desktops (Microsoft Hyper-V)?

What will be an ideal response?

VMware's instant clone desktop feature, known as pooled virtual desktops in Hyper-V, are similar in function to linked clones. When using instant clone desktops the user desktop is created "on the fly" from a master that is running on the host hypervisor. Because they are created in memory, instant clone desktops do not require any disk storage, but are nonpersistent as they are deleted from memory after the user ends their session.