Which of the following describes the installation of an OS contained entirely within another OS...

The installation of an OS contained entirely within another OS installation is described as a guest. A guest is a term that refers to a virtual machine (VM) that runs on top of a host operating system (OS) using a hypervisor or a virtualization software. A guest can have a different OS than the host, and can run multiple applications or services independently from the host. A guest can also be isolated from the host and other guests for security or testing purposes.