What is meant by resistivity and …

Resistivity is the electrical resistance of a conducting material per unit length. In other words, it is the degree to which a conductor opposes the flow of electricity through itself, instead allowing the energy to flow out of the electrical circuit, most often as heat. Resistivity is useful in comparing various materials based upon their ability to conduct electrical currents. The unit of resistance is the ohm.
Conductivity, by contrast, is the degree to which a conductor allows the flow of electricity through itself. The unit of conductivity is the siemens (S). It was formerly called the mho. Good conductors retain heat, minimizing the loss of energy from the electrical circuit. Copper wires, for example, are a material with excellent conductivity. Materials such as air, cloth, or rubber have very poor conductivity.