NVR is to distinguish it from DVR, Digtal Video Recorder (ironically it's not really digital, more like analog) It's much cheaper than NVR, because the camras are simple and diffrere the encoding to the DVR unit. And there XVR wich can combine both Network and Digital cameras

Which is odd because the first time I heard the term DVR was in the late 1990's, referring to the box that was used to record TV signals digitally for playback and/or ad-skipping. The term distinguished it from things such as VCRs, which recorded in analog, on tape. Those DVRs were, in fact, digital.

If the recorder uses digital video as its storage, it's a real DVR, even if the video input is that weird HD variant of NTSC that's everywhere in security cameras