Lets Get Familiar With All The Terms.
CCTV (Closed Circuit Television): This is the older style of video camera surveilance. These were typically low resolution analog cameras that were hard wired directly into a TV display that would show the video feeds from all the cameras. You ussually would have to hook up an external recording device, such as a VCR, to record any of the video feeds. This has been replaced with newer digital systems with DVR's.
Digital Video Recorder (DVR): This is the next generation of video recording. It is all digital which means that you can download the recording to other devices such as computers, smartphones and tablets as well as view the recordings over the internet. Cameras don't necessarily have to be directly connected to the DVR to be able to record the feed from them as newer DVR's have the ability to communicate with cameras over computer networks or even the internet. This name is also interchangeable with devices that record TV feeds as well.
Network Video Record (NVR): This is almost identical device to a DVR, except it can only record video from IP cameras over a computer network, including the internet.
Cloud DVR: This is an internet hosted service where your camera feeds are recorded to server located in the cloud, or internet, instead of being stored locally in a DVR on your premises. The advantage to this service is that you do not have to maintain any hardware or worry about doing any backups of your video recordings.
IP Camera: An Internet protocol camera, or IP camera, is a type of digital video camera commonly employed for surveillance, and which, unlike analog closed circuit television (CCTV) cameras, can send and receive data via a computer network and the Internet.
CCTV Camera: CCTV (closed-circuit television) is a TV system in which signals are not publicly distributed but are monitored, primarily for surveillance and security purposes. CCTV relies on strategic placement of cameras, and observation of the camera's input on monitors somewhere.
Analog Signal: Sound is naturally an analog signal. An analog signal is continuous, meaning that there are no breaks or interruptions. One moment flows into the next. If you were to hum a descending note, people hearing you would be able to detect the change in pitch, but not point to specific moments when the pitch jumped from one note to the next.
Digital Signal: Digital signals are not continuous. They use specific values to represent information. In the case of sound, that means representing a sound wave as a series of values that represent pitch and volume over the length of the recording. In a primitive digital recording of that descending note you hummed, you'd hear a single long sound as a collection of shorter sounds.