1. Cameras - wireless, wired, varifocal, fixed lens, etc. Cameras need a power source to operate; it could be either a regular power line connection or a battery pack -- depending on the camera's design. 2. DVR - Digital Video Recorder - standalone or built in. The "brain" of the surveillance system. Receives recordings from the cameras and allows managing these according to its features (continuous recording, motion activated, etc.) Stores recordings on its hard disk. Most DVRs are networkable and allow remote Internet viewing. 3. Monitor - standalone, your computer 4. Cables and connectors - to connect the cameras to the DVR, and the DVR to the monitor. Wireless cameras do not require cables for connection to the DVR but Wireless Receivers are needed to receive the camera's recordings. These receivers will be connected to the DVR.