NVR; Network Video Recorder is a system that records incoming videos into digital storage areas like USB, computer discs etc.
It is being used in IP surveillance workflows.
It uses the network input. Not takes directly from capture cards like DVRs.
DVR encodes and precosses the video itself.
NVR does those in camera then streams to NVR thru the network. It is being stored in NVR, processed, metadatas are being added and all the desired processes in these side.
NVR systems used for home security; usualy are wireless, have easy setup, have access from web browser, warns users with email, capable of setting visual sensors etc.