VPS is the abbreviation for the term Virtual Private Server. As this name suggests, there is a difference between VPS hosting and shared hosting. The system can run multiple virtual machines (the VPS) on a physical server. So you can use all the advantages and features of a dedicated server, just in a virtual form. Virtual machines have long been used by computer giants like IBM and HP, but VPS hosting is also gaining in popularity among Internet hosting providers.
I was in a similar situation about a year ago, had a managed VPS for some years before i needed a better server and had to switch to an un-managed VPS. Although i had another un-managed VPS without a control panel previously, this time round i chose an un-managed box with cPanel already installed. This was quite handy as i didn't have to deal with installing and licencing the control panel. As have always used cPanel, setting up sites, databases, DNS and all the other configurations was straight forward and fast.
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.