Good Post by Romain Decker (thank you)

My first contact with vMotion goes back to a demo in 2004. I can still remember how the presenter connected to a Windows VM in RDP, launched a movie, migrated the VM to another host and powered off the 1st ESX…and the movie was still running!

VMware vSphere live migration, or vMotion, allows you to move an entire running virtual machine from one physical server to another, without downtime.

Read on here