What is a Virtual Private Server?
A Virtual Private Server (VPS) is an entire operating system that runs within another operating system. It will share system resources like the CPU and RAM with other users but the resources are allocated in such a way that you cannot tell that the system has anyone else on it, much like a dedicated server. So resources are usually setup in such a way that each hosting client is only allowed to use an allocated percent, meaning that resources assigned to you will always available to you. Each virtual server looks and acts like a dedicated server.
So for instance, there may be a server with 2GB RAM, 100GB of disk space and 2 x 2GHz processors with 10 VPSes on it. Each one is guaranteed to have access to 200MB RAM, a disk space limit of 10GB, and an effective CPU of 400Mhz.
There are a number of virtualization technologies, which make this all possible. There are commercial companies such as http://www.vmware.com VMWare, http://www.xensource.com/ XEN.
Like an emulator, VMware software provides a completely virtualized set of hardware to the guest operating system. VMware software virtualizes the hardware for a video adapter, a network adapter, and hard disk adapters. The host provides pass-through drivers for guest USB, serial, and parallel devices.
In essence, virtualization lets you transform hardware into software. Use software such as VMware ESX Server to transform or virtualize the hardware resources of an x86-based computerincluding the CPU, RAM, hard disk and network controllerto create a fully functional virtual machine that can run its own operating system and applications just like a real computer.
Multiple virtual machines share hardware resources without interfering with each other so that you can safely run several operating systems and applications at the same time on a single computer.