"'Containers' are a form of lightweight virtualization as
represented by projects like OpenVZ. While virtualization creates a
new virtual machine upon which the guest system runs, containers
implementations work by making walls around groups of processes.
The result is that, while virtualized guests each run their own
kernel (and can run different operating systems than the host),
containerized systems all run on the host's kernel. So containers
lack some of the flexibility of full virtualization, but they tend
to be quite a bit more efficient.
"As of 2.6.23, virtualization is quite well supported on Linux,
at least for the x86 architecture..."