A Virtual Machine (VM) is a software-based emulation of a physical computer that runs an operating system and applications just like a real machine. VMs are created and managed by a hypervisor, software that sits between the physical hardware and the virtual environments, allocating CPU, memory, storage, and network resources to each VM. This virtualization technology enables multiple isolated operating systems to run simultaneously on a single physical server, maximizing hardware utilization and flexibility.
There are two primary types of hypervisors that power virtual machines. Type 1 (bare-metal) hypervisors like VMware ESXi, Microsoft Hyper-V, and KVM run directly on the host hardware, offering superior performance and are the standard in data centers and cloud infrastructure. Type 2 (hosted) hypervisors like VirtualBox and VMware Workstation run on top of a conventional operating system and are commonly used for development and testing environments.
Virtual machines serve numerous purposes in software development and IT operations:
- Cloud computing: major providers like AWS (EC2), Azure, and Google Cloud Platform deliver infrastructure primarily through VMs
- Development environments: developers create VMs to test software across different operating systems and configurations
- Server consolidation: running multiple workloads on fewer physical servers reduces hardware and energy costs
- Isolation and security: VMs provide strong boundaries between workloads, containing potential security breaches
- Disaster recovery: VM snapshots and migrations enable rapid backup and restoration of entire systems
While containers have gained popularity as a lighter-weight alternative for many use cases, VMs remain important when full operating system isolation is required, when running workloads that need different OS kernels, or when strong security boundaries are necessary. Many modern architectures use both technologies together, running containers inside VMs to combine the efficiency of containerization with the security isolation of virtualization.