What Are Virtual Machines?
A virtual machine (VM) is a simulated computer running inside your real computer. It has its own virtual CPU, memory, storage, and network — everything a physical computer has, but created entirely in software. This lets you run multiple operating systems on a single machine.
How Virtual Machines Work
Special software called a hypervisor creates and manages virtual machines. The hypervisor allocates portions of your physical hardware to each VM. If your computer has 16 GB of RAM, you might give 4 GB to a virtual machine while keeping 12 GB for your main system.
Think of a hypervisor like an apartment building manager. The building (your physical computer) has limited resources — space, electricity, water. The manager allocates these resources to each apartment (virtual machine), ensuring everyone gets what they need without interfering with neighbors.
There are two types of hypervisors:
- Type 1 runs directly on hardware (used in data centers)
- Type 2 runs on top of your existing operating system (what you'd use on your laptop)
Popular Type 2 hypervisors include VirtualBox (free), VMware Workstation, and Parallels (for Mac).
Why Developers Use VMs
Virtual machines solve real problems:
- Cross-platform development — Mac users can run Windows to test software; Windows users can learn Linux
- Safe experimentation — Try risky software without endangering your main system
- Multiple environments — Test your application on different operating system versions
- Isolation — Keep work projects completely separate from personal files
VMs vs Containers
You'll also hear about containers. The key difference: VMs include a complete operating system (heavy, gigabytes in size), while containers share the host's OS kernel (light, megabytes in size). VMs provide stronger isolation; containers start faster and use fewer resources.
Both tools have their place. VMs shine when you need a completely different operating system. Containers excel at packaging applications consistently.