SQL Server virtualization, often achieved through virtualization technologies like Hyper-V or VMware, allows you to run multiple SQL Server instances on a single physical server. This contrasts with traditional deployments where each SQL Server instance requires its own dedicated hardware. This approach leverages the underlying virtualization layer to create isolated environments for each instance, effectively partitioning the physical resources. This virtualization approach offers significant advantages in terms of resource utilization and flexibility. For example, you can easily scale resources up or down based on demand by adding or removing virtual machines. This is particularly useful in cloud environments or situations where you need to manage multiple databases with varying resource requirements.