Define resistance

The property of a conductor by virtue of which it opposes the flow of electric current through it is called resistance. It is given by the ratio of voltage applied to the electric current which flows through it.

R = V/I

Materials which offer very low resistance are called conductors while materials which offer high resistance are called insulators. Higher is the resistance lower is the flow of current. Resistance is dependent on the type of material and its dimensions (area of cross section)