If you open Terminal Server Client, you will see Protocol option (RDP, RDPv5, VNC), RDP and RDPv5 are for rdesktop connection. Terminal Server Client (Applications > Internet > Terminal Server Client) is a GUI front-end to VNC and rdesktop.
See comparison of remote desktop software (). VNC works on almost all operating systems. But there is a way to use VNC with encrypted connection (). VNC is slow compared to rdesktop and VNC connection is unencrypted while rdesktop connection is encrypted by default. There is another similar program called VNC.
Rdesktop and VNC and Terminal Server Client (comparison) In other words, while you are sitting in front of your Ubuntu computer at home, you can log into and access your Windows computer as if you are sitting in front of the Windows computer.
Rdesktop is a client program that allows you to connect from your Ubuntu computer to your Windows computer to remote control the Windows computer.
