What is a virtual machine?

A virtual machine (VM) is a software simulation of a complete computer. It runs inside another computer as an application, but from the inside behaves exactly like a real, separate machine — with its own OS, files, and network settings.

Your physical computer runs Windows. A VM app (VirtualBox, VMware, Parallels) creates a sandboxed environment where Ubuntu Linux runs simultaneously. The two systems do not interfere.

Why use VMs:

• Run software that requires a different OS
• Test safely without risking your main system
• Isolate environments for security research
• Run multiple server environments on one physical machine
• Easy backup and restore (snapshots)

Difference from Docker: a VM includes its own full OS kernel. A container shares the host's kernel. VMs are heavier but more fully isolated.