The web and server hosting world is full of abbreviations that look as though they were designed to confuse inexperienced hosting clients: IaaS, PaaS, SSD, SSL, VPN, VPS, and many more. It’s especially confusing when abbreviations are similar, but mean completely different things, as is the case with VPN and VPS. I’ve often heard hosting clients say VPN when they mean VPS, and vice versa.
OpenVZ virtualization is an OS level container-based virtualization, and it has resources that are divided between users on a physical server. Each container acts like a stand-alone virtual server and can be accessed with a root (SSH) connection. As a separate server container can be rebooted separately, it also has a dedicated IP address, shared RAM, individual processes, files, applications, system libraries and configuration files. On OpenVZ, the kernel cannot be modified. It has its stable version and modules cannot be added. The good thing regarding this virtualization is a faster performance, and a lower need of resources.
The force driving server virtualization is similar to that which led to the development of time-sharing and multiprogramming in the past. Although the resources are still shared, as under the time-sharing model, virtualization provides a higher level of security, dependent on the type of virtualization used, as the individual virtual servers are mostly isolated from each other and may run their own full-fledged operating system which can be independently rebooted as a virtual instance.