Before you start
Nothing required, though Desktop & Server OS Administration gives useful context for what's actually being virtualised.
CLUSTER 0.7
Virtualisation is the single idea underneath almost everything "the cloud" actually is: running many separate, isolated computers on one physical machine, safely, at the same time.
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Think of it as: the long-standing industry standard for running VMs on your own hardware
ESXi is VMware's bare-metal hypervisor — software that runs directly on server hardware to host virtual machines. Worth knowing as you research this: Broadcom acquired VMware in late 2023, and has since discontinued the old perpetual-license tiers (Standard, Enterprise Plus) in favour of subscription bundles. If you're building a home lab or comparing options in 2026, expect a genuinely different licensing conversation than older tutorials describe.
Think of it as: Microsoft's own answer to VMware, built into Windows
Hyper-V ships with Windows Server (and Windows 10/11 Pro) and is the foundation Microsoft's own hybrid infrastructure — including Azure Local, covered in the Hybrid, Endpoint & Workplace domain — is built on.
Think of it as: a complete, isolated computer that happens to live inside another computer
A VM has its own virtual CPU, memory, disk, and OS — completely isolated from other VMs on the same physical host, even though they're sharing the same underlying hardware.
Think of it as: a save point in a video game, for an entire computer
A snapshot captures a VM's exact state at a moment in time. Something breaks after an update? Roll back to the snapshot and it's like the update never happened.
Think of it as: real networking concepts, simulated entirely in software
VMs need to talk to each other and the outside world — virtual switches and virtual network adapters recreate physical networking entirely inside the hypervisor, no physical cables involved.
Before virtualisation, one physical server ran one operating system, often using a tiny fraction of its actual capacity. Virtualisation let providers split one powerful physical machine into dozens of VMs sold to different customers — the entire economic and technical foundation Azure, AWS, and every other cloud platform is built on.
REAL-WORLD SCENARIO
A company tests a risky Windows Server update by first taking a snapshot of the VM. The update breaks a critical application. Instead of a multi-hour disaster-recovery process, an admin rolls back to the snapshot from ten minutes earlier — the VM returns to exactly how it was, update-free, in under a minute.