What feature allows virtual machines to quickly move between hosts without downtime?

VMotion is the feature that enables the live migration of virtual machines from one host to another without any downtime. This is achieved by transferring the VM's active memory and execution state in real-time, allowing the virtual machine to continue running while it moves to a new host. VMotion utilizes shared storage and a network connection between the source and destination hosts to ensure a seamless transition, so users experience no interruption despite the underlying VM being relocated.

In contrast, while Storage DRS optimizes the placement of virtual disks and datastores by balancing workloads and automating storage management tasks, it does not provide for the live movement of VMs between hosts. VMware High Availability focuses on minimizing downtime due to host failures by automatically restarting VMs on other available hosts but does not facilitate the live migration of running VMs. Snapshots capture the state of a VM at a certain point in time but are not involved in moving VMs between hosts and do not allow for live migration.