Jessie Frazelle reiterates her point on containers in the blog post “Setting the Record Straight: containers vs. Zones vs. Jails vs. VMs“:
The Design of Solaris Zones, BSD Jails, VMs and containers are very different.
Solaris Zones, BSD Jails, and VMs are first class concepts. This is clear from the Solaris Zone Design Spec and the BSD Jails Handbook. I hope it can go without saying that VMs are very much a first class object without me having to link you somewhere :P.
Containers on the other hand are not real things.
A “container” is just a term people use to describe a combination of Linux namespaces and cgroups. Linux namespaces and cgroups ARE first class objects. NOT containers.