What is a VNC Server

[Batistabomb]

Guys does anyone has an idea why we use an vnc (virtual network computing) server

[Sukhdeep Singh]

Well i use VNC Viewer a lot. In Layman terms, it is like Windows Remote Desktop but it is cross platform...more here
http://www.realvnc.com/vnc/index.html

VNC - the original cross-platform remote control solution

VNC stands for Virtual Network Computing. It is remote control software which allows you to view and fully interact with one computer desktop (the "VNC server") using a simple program (the "VNC viewer") on another computer desktop anywhere on the Internet. The two computers don't even have to be the same type, so for example you can use VNC to view a Windows Vista desktop at the office on a Linux or Mac computer at home. For ultimate simplicity, there is even a Java viewer, so that any desktop can be controlled remotely from within a browser without having to install software.

VNC is in widespread active use by many millions throughout industry, academia and privately. There are several versions to choose from, including a free version and some substantially enhanced commercial versions.