It is a cross- platform screen sharing system that was created to remotely control another computer. VNC stands for Virtual Network Computing.

Both technologies use direct peer-to-peer communication.All you need to know about VNC remote access technology What is VNC?.

Both RDP and VNC technologies require client side and server side software to support communication.

And if you're both trying to use the computer at the same time, it's

VNC has security implications if you remote into a machine that an Administrator is logged into, you'll effectively be an Administrator.

Consequently, when several users (including the one operating the real physical monitor and keyboard) connect to the same server they see the same thing and they type on the same keyboard.

VNC connects a remote user to the computer itself by sharing its screen, keyboard and mouse.

VNC follows the older model of simply showing whatever is on the screen with no forced logins required.

It is an open platform independent graphical desktop sharing system designed to remotely control another computer.

VNC stands for Virtual Network Computing.

RDP supports multiple monitors, if the client has them.

RDP can support multiple remote users logged in to the same server that completely unaware of each other.

RDP works in the same way as if the user had logged in to the physical server directly.

RDP logs in a remote user to the server computer by effectively creating a real desktop session on the server computer including a user profile.

It is a proprietary protocol built by Microsoft to let users to graphically control remote computer.

RDP stands for Remote Desktop Protocol.

Adding a bit of information on other answers which I found while doing a research,

Nx vs vnc