VNC stands for Virtual Network Computing. It is remote control software which allows you to view and fully interact with one computer desktop using a VNC viewer on another computer desktop anywhere on the LAN or Internet. The two computers don't even have to be the same type, so for example you can use VNC to view a Windows XP desktop at the office on a Linux or Mac computer at home.
Once you are connected, traffic between the viewer and the server is unencrypted, and could be sniffed by someone with access to the intervening network. Is security imported to you, we recommend tunneling the VNC protocol through some more secure channel such as SSH. This workshop describes how to connect from a Windows XP client to a Linux (OpenSuse 10.3) server via VNC and to tunnel this connection using SSH.