In this category are listed web hosting providers who offer Virtual Private Servers (VPS),
Virtual Dedicated Servers (VDS).
VPS it's system that allow to have many "virtual" separate servers on one computer.
For end-customers they work as a real Dedicated servers (root access, can install own software and modules etc), but really there are few customers on one real server.
More about Virtual Private Servers
Virtual private servers are also known as Virtual dedicated servers. They display a form of virtualization that split a single physical server into multiple virtual servers. This practice of dividing a single virtual server to make it appear as multiple virtual servers has been commonly observed in mainframe computers. However it has seen a sudden appearance lately with the development of software and technologies such as VMware, Xen, FreeBSD Jail, User-mode Linux, Linux-VServer, FreeVPS, OpenVZ, and Virtuozzo.