NDI (Network Device Interface) is a technology that allows video devices, such as cameras and video mixers, to communicate with each other over a network. It enables the devices to share and receive video streams, as well as other data, in real-time. This makes it possible for video from multiple devices to be combined and manipulated in a variety of ways, such as mixing, switching, and compositing. NDI is commonly used in live video production and broadcasting, as well as other applications that require the ability to share and manipulate video streams over a network.