Pre-configured and ready to use virtual servers
VDS (Eng. Virtual Dedicated Server) or VPS (Eng. Virtual Private Server) - a virtual server is based on the KVM or OpenVZ virtualization technology. Every VPS runs an autonomous copy of kernel, which is completely independent of the kernel and operating system of the host server. Almost any operating system can be installed on the VPS server. By purchasing this service you get a fully configured, ready to use VPS server, without a need to invest money into expensive server hardware.
VPS allows you to have administrative (root) access, to install and customize any services, to manage settings of firewall, etc.
Briefly speaking, VPS is almost a dedicated server at more affordable price just a bit less powerful. This gives VPS servers an advantage over shared hosting services or expensive dedicated servers.