OS System-level Virtualization mainly defines virtualizing a physical server at the operating system whcic enables multiple isolated and secured virtualized servers to run on a single physical server.
The New environment share the same OS as the main system. Some of the examples are Linux-VServer, Virtuozzo for Linux VPS Hosting or Windows VPS, openVZ, Solaris Containers and FreeBSD Jails.
Virtuozzo is known to be one of the best virtualization software for hosting a Virtual Private Server