VMware Workstation Player course
What Is a Virtual Machine? Virtual Hardware, Hypervisors, Hosts, and Guests Explained
Learn how virtual machines use virtual hardware, how hosts and guests differ, and how Type 1 and Type 2 hypervisors compare, including VMware Workstation Player.
A virtual machine (VM) is a software-defined computer. It can boot and run its own operating system and applications, much like a physical computer. The operating system inside the VM is called the guest operating system.
From the guest operating system's perspective, the VM looks like a computer with a processor, memory, storage, networking, and other devices. Those devices are virtual rather than separate physical components. The virtualization software maps them to resources provided by the real computer.
Host, Guest, and Hypervisor: The Essential Vocabulary
Several terms describe the different layers involved in virtualization:
- Physical hardware: The actual CPU, RAM, storage, network interfaces, display hardware, and other devices in the real computer.
- Host: The physical computer on which virtualization software runs. In desktop virtualization, “host” can also refer to the host operating system.
- Host operating system: The primary operating system installed on the physical computer. In a Type 2 setup, it runs the virtualization application.
- Hypervisor: The virtualization layer that creates, runs, and manages VMs while coordinating their access to physical resources.
- Virtual machine: The software-defined computer created by the hypervisor.
- Guest: The VM or, depending on context, the operating system running inside the VM.
- Guest operating system: The OS installed and running inside a VM.
The host and guest are separate operating-system environments. For example, Windows can be the host operating system while Linux runs as the guest operating system inside a VM.
What Hardware Does a VM Have?
When a VM starts, the hypervisor presents it with a set of virtual hardware. The guest OS detects and uses these devices as if they were hardware in a physical computer. The VM's hardware is configured in its settings, and each allocation is backed by capacity or devices on the host.
Virtual hardware does not create extra physical capacity. Assigning four virtual processors does not give the host four new physical CPUs, and configuring a large virtual disk does not automatically reserve that much free space unless the disk format and allocation settings require it.
How the Host Provides Physical Resources
The host computer supplies the resources used by its VMs:
- Processor time: The hypervisor schedules VM work on the host CPU.
- RAM: Memory assigned to a VM comes from the host's available memory.
- Storage: Virtual disk files, configuration files, snapshots, and guest data occupy host storage.
- Networking: Virtual network adapters use host networking services and may share a physical Ethernet or Wi-Fi adapter.
- Hardware devices: USB devices, displays, sound hardware, and removable media can be presented to the guest through virtualization features.
Multiple VMs can share the same host. The hypervisor allocates and schedules resources so that each guest can operate, but every allocation is limited by the host's capacity. The host also needs resources for its own operating system and applications.
Over-allocation can harm both environments. Assigning too much RAM can force the host to use slower storage or leave too little memory for host applications. Assigning too many virtual CPUs can increase scheduling overhead and leave the host unresponsive. Heavy disk activity from a VM can also slow other programs using the same storage.
What Is a Hypervisor?
A hypervisor is software that creates, runs, and manages virtual machines. It mediates access between guest systems and physical hardware. Its responsibilities include presenting virtual devices, allocating CPU and memory, connecting virtual disks to host storage, and providing virtual networking.
The hypervisor also gives a VM some independence from a particular physical hardware configuration. A VM's operating system interacts with the virtual hardware defined by the VM rather than directly depending on every component in the original computer. This can make a VM easier to move or reproduce on compatible hosts.
That independence has limits. A VM still requires a host with enough CPU, RAM, storage, compatible virtualization support, and suitable device access. Virtualization abstracts hardware; it does not remove the need for hardware.
Type 1 Hypervisors: Bare Metal
A Type 1 hypervisor, also called a bare-metal hypervisor, runs directly on physical computer hardware rather than as an application on top of a conventional desktop operating system.
Type 1 designs are common on dedicated servers, in data centers, and in enterprise environments. The hypervisor is the primary software layer that controls the hardware and hosts one or more guest operating systems. Management tools may run elsewhere or be provided as additional components, but the core virtualization layer is not dependent on a general-purpose desktop OS.
Representative examples include VMware ESXi, Microsoft Hyper-V Server, and Xen-based platforms. Product editions, deployment models, and architectures can vary, so the name of a product alone does not describe every feature or installation option.
Type 2 Hypervisors: Hosted Virtualization
A Type 2 hypervisor, also called a hosted hypervisor, is installed as an application inside an existing host operating system. The host OS manages the computer normally, while the hypervisor application creates and runs VMs within that environment.
Type 2 virtualization is common on personal computers. It is useful for learning operating systems, testing software, developing applications, and running another OS without replacing the main installation. Familiar examples include VMware Workstation Player, Oracle VirtualBox, and Parallels Desktop.
Because a Type 2 hypervisor uses services and drivers supplied by the host OS, the stack contains an additional operating-system layer compared with a typical Type 1 deployment.
Type 1 and Type 2 Hypervisors Compared
Type 1 is not universally faster or better than Type 2. Actual performance depends on the workload, hardware virtualization support, drivers, storage, memory pressure, VM settings, and the host's other activity. The most important distinction is where the hypervisor runs and how it is deployed.
Where VMware Workstation Player Fits
VMware Workstation Player is a Type 2 hypervisor. It is installed on a supported desktop host operating system, such as Windows or Linux, and runs as an application in that host environment. Player then creates and runs guest VMs.
The layer relationship is:
- Physical computer: Contains the actual CPU, RAM, storage, network adapter, display hardware, and other devices.
- Host operating system: Runs directly on the physical computer and manages normal desktop applications.
- VMware Workstation Player: Runs within the host OS and provides the Type 2 virtualization layer.
- Virtual machine: Contains configured virtual processors, memory, disk, network, display, and other devices.
- Guest operating system: Installs and runs inside the VM using the virtual hardware.
For a broader product context, see the VMware Workstation Player course. Related lessons cover memory allocation, virtual disks, and VM networking configurations.
End-to-End Example: Windows Host and openSUSE Guest
Imagine a physical laptop running Windows 10 or Windows 11:
- Windows is installed on the laptop's physical storage and is the host operating system.
- VMware Workstation Player is installed as a Windows application.
- In Player, the user creates a VM and installs openSUSE Linux in it.
- The VM is configured with a small, appropriate number of virtual processors, a portion of the laptop's RAM, a file-backed virtual disk, and a virtual network adapter.
- openSUSE boots from the VM's virtual disk and sees the configured virtual CPU, memory, storage, network, and display devices.
- Windows and openSUSE run at the same time, sharing the laptop's physical CPU, RAM, storage, and network connection.
In this example, Windows owns and manages the physical computer. Player presents virtual hardware to the openSUSE guest, while the physical hardware supplies the underlying capacity.
Benefits of Virtualization
- Run multiple operating systems: A single physical computer can run Windows, Linux, or other supported systems in separate VMs.
- Test software: Applications can be installed in a test guest instead of directly on the main host installation.
- Learn operating systems: Students can practice installation, configuration, and administration without dedicating a separate physical computer.
- Separate workloads: Different projects or environments can be kept in distinct VMs with their own files and settings.
- Rebuild test environments: A test VM can often be removed and recreated without reinstalling the host OS.
A VM is isolated to a degree, but it is not automatically immune to security problems, incorrect configuration, malware, defective software, or resource exhaustion. Isolation depends on the hypervisor, guest configuration, integrations, network design, updates, and user actions. Features such as shared folders, clipboard integration, USB access, and bridged networking can create useful connections between host and guest but may also affect the isolation boundary.
Common Misunderstandings and Troubleshooting
The VM is slow and the host is unresponsive
The VM and host are competing for finite CPU, memory, and storage resources. Too much assigned RAM or too many virtual CPUs can negatively affect the host. Reduce the VM's allocations where appropriate, close other host applications, and check whether the host storage is busy or nearly full.
The guest OS is confused with the host OS
The host OS runs directly on the physical computer. The guest OS runs inside the VM, usually visible through a VM window or virtual display. In a VMware Workstation Player setup, Player sits inside the host OS; it is not the guest OS.
The VM is expected to have independent physical hardware
The VM receives virtual hardware. That hardware is ultimately backed by the host's physical resources and devices. Configurable virtual devices cannot exceed the host's available CPU, RAM, storage, networking, or hardware compatibility.
VMware Workstation Player is mistaken for a Type 1 hypervisor
Player is installed inside a conventional host operating system and runs as a desktop application. That placement makes it a Type 2 hypervisor, even though it still performs important virtualization and resource-management work.
Exam-Relevant Summary
- A VM is a software-defined computer that can run its own OS and applications.
- The guest OS sees virtual CPU, memory, disk, network, display, and other devices as its hardware.
- The host is the real computer and, in desktop virtualization, usually includes the host OS running the virtualization application.
- The hypervisor creates and manages VMs and mediates access to physical resources.
- A Type 1 hypervisor runs directly on physical hardware.
- A Type 2 hypervisor runs as an application on a host OS.
- VMware Workstation Player is a Type 2 hypervisor.
- Virtualization enables multiple environments but does not create unlimited resources or guarantee complete isolation.