Doubt understanding OpsCenter 12c documentation - Using Zones x BEs

Hello,
Could you, please, explain the following excerpt?

"Do not use the software to create or manage zones if your site uses Boot Environments to update operating systems of zones.
Alternate Boot Environment (ABE) is not supported for zones or for the Enterprise Controller or Proxy Controller systems."
Ref: 2 Preparing Your Environment - Using Zones

Does it mean Solaris 10, 11 or both?
What is meant by "operating systems of zones"?
I've heard that BE were supported. So, they aren't supported after all?

Thanks in advance,
Carlos.