## Introduction to Virtualization

**Virtualization** is the magic that runs the cloud.
It allows one physical computer (Host) to run multiple fake computers (Guests).

### Physical vs Virtual
*   **Physical**: One OS controls the hardware directly. If the OS crashes, the machine stops.
*   **Virtual**: A **Hypervisor** sits between the hardware and the OS.
    *   It slices the RAM (16GB -> 4GB for VM1, 4GB for VM2).
    *   It slices the CPU time.

### Why do we use it in Security?
1.  **Isolation**: If you run malware in a VM, it cannot infect your real laptop (usually).
2.  **Snapshots**: You can save the state. If you delete `System32` by accident, just click "Revert".
3.  **Efficiency**: You can run a Windows DC, a Linux Web Server, and a Kali Attacker all on one laptop.