Do you think that Virtual Private Server also known as VPS is a
popular and a new concept? No it is an old concept of dividing a
physical device, which is large and costly into many parts and
allowing more and more people access to it at affordable price. It is
just more than shared server and less than a dedicated servers.
Virtual Private Server is similar to a building, which is divided into
different flats, and each flat is independent unit having its own
drawing room, kitchen and its own lock and key.
Please read more here
http://www.jpstream.net/articles//articles/1379/1/Virtual-Private-Servers-Their-Avantages/Page1.html