This post is about the vSphere 6 product feature vMotion. 
The first time I saw a vMotion between two hosts it was amazing. Not only doing it without down time, but while the server was up and functional!
Now we have not only vMotion cross vSwitch but cross vCenter and even Long Distance. If I was told 25 years ago that I'd be able to move a server while it was up from one data center to another in another State or Country, it would have seemed impossible and far fetched.
vMotion is the live migration of virtual machines from one physical host to another with no downtime or service interruption.
The three different editions of vSphere supply different vMotion functionality.
vSphere Standard - cross vSwitch vMotions
vSphere Enterprise & vSphere Enterprise Plus - cross vSwitch, cross vCenter, and Long Distance vMotions