A coaxial cable consists of two concentric conductors, which are seperated by a dielectric and by a screen. Fields of applocation for coaxial cables are video technology, electrical measurement as well as applications, where radio signals have to be transferred without loss.

A double screened coaxial cable is presented here
Structure of a double screened coaxial cable:
1   = inner conductor – solid wire or stranded wires (1b)
2   = dielectric / isolation
3a = braid or foil
3b = braid or foil
4   = outer sheath

more information about the structure of such cables: Structure coaxial cable