A network video recorder (NVR) is a specialized computer system that includes a software program that records video in a digital format to a disk drive, USB flash drive, SD memory card or other mass storage device.
An NVR contains no dedicated video capture hardware. However, the CPU and graphics processing unit (GPU) of the NVR performs the encoding for compression and decompression of the video streams. The bitrate of the encoded video stream is variable and is determined by the capabilities of the CPU and GPU. The disk drives store the recorded video streams as data files.
The main purpose of an NVR is to record video from security cameras so that the footage can be reviewed later if needed. Most NVRs also include features such as motion detection, email alerts, remote viewing and playback, and RAID storage for redundancy.
Frequently Asked Question
Does NVR need to be connected to router?
If a CCTV DVR or NVR don’t have a built-in WiFi support, then you have to run internet cable (CAT 5 or CAT 6 Ethernet cable) to connect your DVR or NVR to the internet via the router. Of course, by using another WiFi router/access point as a wireless bridge, you could connect a CCTV DVR to your router wirelessly.21 July 2021 
NVRs are a great way to keep an eye on your home, but they don’t need to be connected to your router. You can connect them directly to your modem or even use a mobile hotspot. Just make sure you have a good connection and plenty of bandwidth.