CentOS is one of the most popular Linux distribution for dedicated servers. This is largely because it provides the functionality and stability of Red Hat Enterprise Linux without the licensing and support fees.
OpenVZ is a free and open source virtualization solution that you can use to create virtual private servers (VPS). In OpenVZ’s terminology, these VPS instances are called “containers”. The benefit is that you can run multiple instances of CentOS, each behaving as a separate server with root access only within the container.
OpenVZ provides OS virtualization, meaning that you can only virtualize Linux on a Linux server. For virtual machines or hardware virtualization, you would need another solution such as VMware Server, Parallels Workstation, Virtualbox, KVM, or Xen. OpenVZ makes it easy to scale and create efficient virtual private servers. OpenVZ is largely viewed as a legitimate free alternative to Parallels Virtuozzo Containers.
The CentOS website has an installation guide for OpenVZ. You can install it with YUM, but will need to disable SELINUX if you have it running. The official YUM repository is provided by OpenVZ. Initial installation and container creation will require some command-line experience, but once it is up and running, there are some web-based frontends you can use to monitor and manage containers.