There are basically two main types of CCTV systems. One is ‘Analogue’, and the other is ‘Digital’. In terms of recording, they are both stored digitally in a hard disk.
An analogue camera sends its signal electrically via a co-axial cable to a Digital Video Recorder (DVR) which converts the signal into a digital format and stores it in the hard disk with a time stamp so you can access the video by searching its catalogue at a later time.
Internet Protocol (IP) camera, on the other hand, converts the analogue signal at the camera itself, and if necessary, transmit the video feed digitally to a Network Video Recorder (NVR) which then records it with a time stamp. Since the camera has already done the processing and being a networking device itself, that means you can connect a PC or handphone directly to the camera to view the image. Some IP Cameras even have a built-in memory card where it can store video recordings, albeit recordings are limited as an SD card has limited storage compared to a hard disk.