Paravirtualisation is a technique used to obtain high performance virtualisation by presenting a very thin hardware compatability layer to guest operating systems. This requires modification in the guest operating systems, but allows for near-native performance and a comparatively simple hypervisor. See Wikipedia for more info.
Xen is one implementation of paravirtualisation and is the technology that BitFolk uses.
Our VPS offerings are all unmanaged. This means that we provide you with the VPS and a barebones install of your chosen distribution, then you are responsible for the installation, configuration and management of the operating system and all your applications from that point on.
Our services are designed with technically proficient people in mind, who are perfectly capable of managing their own UNIX-like servers. If you need someone to manage your server(s) then our services are not for you, but we could probably suggest some companies who do provide managed hosting or systems administration consultancy.
Virtual Private Server. A server that appears to be running on dedicated hardware, but in fact is one of many running on the same physical hardware via some virtualisation method. BitFolk VPSs use the Xen paravirtualisation system, but there are many kinds of virtualisation in use. Wikipedia has a good article on this subject.