3.1 What virtualization is, and what a hypervisor does
You're about to run a domain controller, a Linux server and an attacker machine on the computer you're reading this on. Before you do, it's worth having a one-sentence answer to what that actually is, because "I set up some VMs" and being able to define virtualization are different things in an interview.
Virtualization is using software to divide one physical computer into several independent computers, each running its own operating system, each isolated from the others, and each behaving as though it owns real hardware.
Three words in that sentence are doing the work.
Divide. One machine's CPU, memory and disk get carved into portions and handed out. Nothing is copied or emulated in the slow sense; the guest's instructions mostly run directly on your real processor.
Independent. Each virtual machine boots, runs and crashes on its own. You can reboot one without touching the others, and that's what makes a lab like this one possible rather than a single computer you keep reinstalling.
Isolated. A guest cannot see the others or reach into the host except through channels you deliberately open. That's why you'll shortly run malware-adjacent tooling on Kali next to a domain controller without fear, and it's why the offensive work in Module 14 is safe to do at all.
Organizations virtualize for reasons you'll feel in this course: one physical server can do the work of many, machines can be created in minutes instead of ordered in weeks, and a broken system can be rolled back to a snapshot instead of rebuilt. You'll experience that last one personally in lesson 3.5.
Worth knowing that the idea generalizes well beyond servers. Module 4 virtualizes networks, building switches and segments that exist only in software. Module 6 introduces containers, which chase the same isolation with a lighter mechanism. Storage and desktops get the same treatment in industry. The pattern is always identical: a layer of software presents something that looks like dedicated hardware, backed by shared real hardware underneath.
The program that does it
A hypervisor is a program that lies to operating systems. It presents each guest OS with what looks like a computer (a CPU, some RAM, a disk, a network card) and secretly maps all of it onto slices of your real hardware. The guest can't tell. Windows Server will boot inside your desktop or laptop genuinely believing it's on a rack somewhere, and that belief is what the virtualization setting you checked in 0.6 makes efficient: your CPU has instructions specifically built to keep guests fast and contained.
Two flavors exist, and the names come up in interviews. A type 1 hypervisor runs on bare metal with no OS underneath; that's what runs enterprise datacenters (VMware ESXi, Proxmox, Hyper-V Server), and my own lab runs on one. A type 2 hypervisor runs as an application on top of your normal OS, which is what you'll use, because the computer running it also needs to stay your everyday computer.
Why VMware Workstation Pro
This course standardizes on VMware Workstation Pro, and the reasoning is worth stating rather than asserting. It's free now (Broadcom dropped the license fee for everyone in late 2024). It's the desktop sibling of the ESXi/vSphere stack that dominates enterprise virtualization, so its concepts and vocabulary transfer directly to what you'll meet at work. And it's what the course's own screenshots use, which matters for a beginner more than any feature does: when your screen matches the material, you can tell a mistake from a cosmetic difference.
VirtualBox is a fully supported second path. It's open source, it runs the same lab, and if you already use it, keep it. Wherever the two tools genuinely differ, you'll see a callout box like this:
Boxes like this one translate the step for VirtualBox users. If there's no box, the step is the same in both tools apart from cosmetics.
What we're not using, and why, since you'll wonder: cloud VMs cost real money monthly and vanish when you stop paying, while this lab is yours forever and works on a plane. Hyper-V comes free inside Windows but can't run the whole course comfortably and its skills transfer less broadly. Proxmox is wonderful and is the natural next step after this course, when you graduate to a dedicated homelab box and want the type 1 experience.
One honest limitation to carry forward: a type 2 hypervisor shares your computer with everything else you run. Forty browser tabs and three VMs will fight, and the VMs will win, because you gave them their RAM up front. Close what you don't need on lab nights.
What you'll meet at work
You will almost certainly not administer VMware Workstation in a job. You will administer one of these, so it's worth knowing the names before somebody says one in an interview and watches your face.
The reassuring part first: a virtual machine is a virtual machine. Everything Module 3 teaches you (what a hypervisor does, virtual disks, snapshots, virtual network adapters, why you size RAM up front) is the same on every platform below. What changes is the management layer and the scale: instead of one host you have a cluster, instead of a local disk you have shared storage, and instead of shutting a VM down to move it you migrate it while it's running.
- VMware vSphere (the ESXi hypervisor plus vCenter to manage it) has been the enterprise default for two decades. If you join a large organization, this is the most likely thing you'll find. Its position is less certain than it was: Broadcom's acquisition brought significant licensing and packaging changes, and a lot of shops have been actively evaluating alternatives since. That churn is why the rest of this list matters more than it would have a few years ago.
- Microsoft Hyper-V comes inside Windows Server at no extra cost, which makes it common wherever the estate is already Windows. Managed through Windows Admin Center, Failover Cluster Manager, or System Center. You are already running Windows Server in this course, so this is the shortest hop from what you'll know.
- Proxmox VE is open source, built on Linux KVM, and has grown sharply, particularly in smaller organizations and among the VMware-alternative crowd. It's also the most likely thing you'll run yourself when you outgrow a laptop and buy a dedicated box. The CyberRack section in the top menu specifies exactly that build, and says what changes if you run the course on it rather than on a laptop.
- Nutanix AHV shows up in hyperconverged environments, where compute and storage are sold as one appliance rather than assembled.
- KVM with libvirt is the Linux-native foundation underneath Proxmox and most public cloud. Worth recognising as the layer, not just a product.
- The cloud providers are running hypervisors too. An EC2 instance or an Azure VM is a guest on somebody else's host; you just never touch the host. That's the whole difference.
The vocabulary changes, the ideas don't
This is the genuinely useful part to carry into an interview, because the same concept has a different name on each platform:
| Concept | VMware | Hyper-V | Proxmox |
|---|---|---|---|
| point-in-time copy | snapshot | checkpoint | snapshot |
| move a running VM | vMotion | live migration | migrate |
| where disks live | datastore | SMB/CSV share | storage pool |
| management console | vCenter | Windows Admin Center | web UI, built in |
Don't go and learn all of these. Recognise the names, know which family
each belongs to, and remember that the concepts underneath are the ones
this module is teaching you. Somebody who understands snapshots properly
can work out checkpoints in an afternoon. Somebody who only memorised
where the buttons are in one product cannot.
If one of them interests you, the vendor documentation is free and the community editions of Proxmox and Hyper-V cost nothing to try.