A DVR is a device that records and stores video footage from analog security cameras. It converts the analog signals from cameras into digital formats and saves them on a hard drive for later retrieval. DVRs are typically used in traditional CCTV (closed-circuit television) surveillance systems, which rely on coaxial cables to connect the cameras to the recorder. An NVR is a device used to record video footage from IP (Internet Protocol) cameras, which send digital video signals over a network. Unlike DVRs, NVRs work with cameras that transmit data through Ethernet cables or Wi-Fi, allowing for more flexible and scalable installations.