Virtual Machines Explained: What They Are and How They Work

Virtual machines are one of the most important technologies behind modern IT infrastructure and cloud computing.

A virtual machine (VM) allows you to run an operating system inside another physical computer as if it were a separate computer.

For example, you can have a Windows computer running:

Windows 11
     ↓
Virtualization Software
     ↓
Ubuntu Linux VM

The Ubuntu system behaves like a real computer even though it is running virtually.

In this article, we’ll explain what virtual machines are, how they work, their advantages and limitations, and why they are important in cloud computing.

What Is a Virtual Machine?

A virtual machine is a software-based computer that runs on a physical computer.

A VM can have its own:

• CPU
• RAM
• Storage
• Network interface
• Operating system
• Applications

The physical computer is called the host, while the virtual machine is called the guest.

Physical Computer
       │
       ├── Host Operating System
       │
       └── Virtualization Software
              │
              ├── VM 1 → Windows
              ├── VM 2 → Ubuntu
              └── VM 3 → Debian

Each VM operates independently from the others.

What Is Virtualization?

Virtualization is the technology that allows physical hardware resources to be divided into virtual resources.

Instead of having one physical server running one operating system, virtualization can allow multiple virtual machines to run on the same physical server.

For example:

Physical Server
┌──────────────────────────────┐
│ CPU: 16 Cores                │
│ RAM: 64 GB                   │
│ Storage: 2 TB                │
│                              │
│ VM 1 → Windows Server        │
│ VM 2 → Ubuntu Server         │
│ VM 3 → Debian Server         │
│ VM 4 → Windows Server        │
└──────────────────────────────┘

The physical resources are shared between the virtual machines.

What Is a Hypervisor?

A hypervisor is software that creates and manages virtual machines.

It controls how physical resources such as CPU, RAM, storage, and networking are allocated to VMs.

There are two main types of hypervisors.

Type 1 Hypervisor

A Type 1 hypervisor runs directly on the physical hardware.

Physical Hardware
       ↓
Type 1 Hypervisor
       ↓
VM 1 | VM 2 | VM 3

Examples include:

• VMware ESXi
• Microsoft Hyper-V
• KVM

Type 1 hypervisors are commonly used in servers and data centers.

Type 2 Hypervisor

A Type 2 hypervisor runs on top of a normal operating system.

Physical Hardware
       ↓
Windows / Linux / macOS
       ↓
Type 2 Hypervisor
       ↓
Virtual Machines

Examples include:

• Oracle VirtualBox
• VMware Workstation

Type 2 hypervisors are commonly used on personal computers for testing, development, and learning.

Type 1 vs Type 2

How Does a Virtual Machine Work?

When you create a VM, you assign virtual hardware to it.

For example:

VM Configuration

CPU: 4 vCPU
RAM: 8 GB
Storage: 100 GB
Network: Virtual NIC
OS: Ubuntu Linux

The hypervisor maps these virtual resources to physical hardware.

For example:

Virtual CPU
     ↓
Physical CPU

Virtual RAM
     ↓
Physical RAM

Virtual Disk
     ↓
Physical Storage

Virtual NIC
     ↓
Physical Network Adapter

The guest operating system sees virtual hardware and uses it just like it would use hardware in a physical computer.

What Is a VM Snapshot?

A snapshot captures the state of a virtual machine at a particular point in time.

For example, before making a major configuration change, you might create a snapshot.

VM Working
    ↓
Create Snapshot
    ↓
Make Changes
    ↓
Problem?
    ↓
Revert Snapshot

Snapshots can be useful for testing and temporary rollback.

However, they should not normally be treated as a replacement for a proper backup strategy.

Benefits of Virtual Machines

1. Better Hardware Utilization

Without virtualization, a physical server might use only a small percentage of its resources.

Virtualization allows multiple workloads to share the same hardware.

2. Isolation

Each VM operates in its own environment.

If one VM has a problem, the other VMs can often continue running.

This isolation is useful for testing and server environments.

3. Easy Testing

You can create a VM and install an operating system without changing your main computer.

For example:

Main PC
  │
  ├── Windows
  │
  ├── Ubuntu VM
  │
  └── Kali Linux VM

This is particularly useful for IT and networking students.

4. Faster Deployment

Creating a virtual server is generally faster than purchasing and installing a new physical server.

5. Easier Migration

VMs can often be moved or replicated between compatible virtualization environments.

This can make infrastructure management easier.

6. Cloud Integration

Virtual machines are heavily used by cloud providers.

When you create a cloud server, you are often creating a virtual machine running on the provider’s physical infrastructure.

Disadvantages of Virtual Machines

Virtualization also has some limitations.

Resource Consumption

Each VM requires CPU, RAM, storage, and network resources.

Running too many VMs can overload the host.

Performance Overhead

Virtualization introduces some overhead compared with running directly on physical hardware, although modern virtualization is highly optimized.

Management Complexity

Large virtual environments can become complex.

Administrators need to manage:

• Hosts
• VMs
• Storage
• Networks
• Backups
• Security
• Monitoring

Single Host Failure

If several important VMs run on one physical server and that server fails, multiple services may become unavailable.

This is why production environments often use redundancy and high-availability solutions.

Virtual Machines in Cloud Computing

Virtual machines are a fundamental part of many cloud platforms.

Instead of buying a physical server, you can create a VM from a cloud provider.

For example:

Cloud Provider Data Center
          ↓
Physical Server
          ↓
Hypervisor
          ↓
┌─────────────────────┐
│ Virtual Machine     │
│                     │
│ Linux               │
│ 4 vCPU              │
│ 8 GB RAM            │
│ 100 GB Storage      │
└─────────────────────┘

You can then install applications and configure networking just as you would with a physical server.

Virtual Machine vs Physical Machine

Virtual Machines vs Containers

VMs and containers are related but different technologies.

A virtual machine includes a complete operating system.

Physical Server
   ↓
Hypervisor
   ↓
VM
   ↓
Guest OS
   ↓
Application

Containers usually share the host operating system kernel.

Physical Server
   ↓
Operating System
   ↓
Container Engine
   ↓
Container
   ↓
Application

Containers are generally lighter and faster to start, while VMs provide stronger isolation and complete operating-system environments.

We’ll cover containers in a future cloud article.

Popular Virtualization Technologies

Some technologies you may encounter include:

VMware

VMware provides virtualization technologies widely used in enterprise environments.

Microsoft Hyper-V

Hyper-V is Microsoft’s virtualization platform and is commonly used with Windows Server environments.

VirtualBox

VirtualBox is popular for desktop virtualization and learning.

KVM

KVM is a Linux-based virtualization technology widely used in servers and cloud environments.

How IT Professionals Use Virtual Machines

Virtual machines are useful for many IT tasks.

Server Testing

Administrators can test server configurations before deploying them to production.

Network Labs

You can create multiple virtual machines to simulate a network.

VM1
 │
 ├──── Virtual Network ──── VM2
 │
 ├───────────────────────── VM3
 │
 └───────────────────────── VM4

Software Testing

Developers can test applications on different operating systems.

Cybersecurity Labs

Security professionals can create isolated environments for learning and testing.

Development

Developers can create consistent environments for their applications.

A Simple VM Lab for Beginners

If you have a reasonably powerful computer, you can create a small laboratory.

For example:

Your PC
│
└── VirtualBox
     │
     ├── Ubuntu Server
     ├── Windows Server
     └── Another Linux VM

You can then practice:

• IP addressing
• DNS
• DHCP
• Active Directory
• Linux administration
• Networking
• Server configuration

This is an excellent way to build practical IT skills without purchasing several physical computers.

Important VM Terms

Here are some terms beginners should know:

Conclusion

Virtual machines allow multiple independent computer environments to run on the same physical hardware.

They are widely used in:

• Data centers
• Cloud computing
• Server infrastructure
• Software development
• IT training
• Networking labs
• Cybersecurity

The most important concepts to remember are virtualization, hypervisors, hosts, guests, and virtual resources.

If you’re interested in cloud computing, understanding virtual machines is an essential foundation.

FAQ

What is a virtual machine?

A virtual machine is a software-based computer that runs on physical hardware using virtualization technology.

What is a hypervisor?

A hypervisor is software that creates and manages virtual machines and allocates physical resources to them.

What is the difference between a host and a guest?

The host is the physical computer running the virtualization environment. The guest is the operating system running inside a virtual machine.

Is a VM the same as a physical computer?

Not exactly. A VM behaves like a computer but uses virtualized hardware provided by a hypervisor.

Can I run Linux inside Windows?

Yes. You can use virtualization software such as VirtualBox or VMware Workstation to run Linux as a virtual machine on Windows.

Are virtual machines used in cloud computing?

Yes. Virtual machines are a fundamental technology used by many cloud platforms to provide computing resources.