The BNC connector is used for RF signal connections, for analogue and Serial Digital Interface video signals and CCTV equipment. It is also an alternative to the RCA connector when used for composite video on commercial video devices.
RG-58 is a coaxial cable that is used for wiring purposes. A coaxial cable, in general, consists of an inner conductor that is surrounded by a spacer. The coaxial cable is electrically charged and sometimes consists of different uninsulated conductors that remain entangled with one another. The insulating spacer of the cable is further surrounded by a sheath that is cylindrical in shape. The final circle is formed by an insulating jacket. The insulation surrounding the RG58 cable carries a low impedance of around 50 or 52 ohms. It is generally used for generating signal connections that are of low power.
Black moulded cable
RG-58/U Coaxial cable
50 Ohm BNC cable