NVR system is a whole set solution of NVR and IP cameras. For some who are using security camera system for the first time, they can avoid the troubles of picking and combine NVR and cameras, also save time to buy additional wiring and other accessories.
NVRs come in various sizes. Typically, you will see these systems in 4, 8, 16 and 32 channel (camera) systems. Having 16 channels will allow you to have 16 cameras on one system. This means you can record 16 cameras on one system. Most people tend to go with 8 or 16 channel recorders because of the large capacity of camera channels they can use. Even if you only need 5 cameras to start, an 8 or 16 channel NVR will allow you to have growing room.