What is Ohm's Law and where is it used?

Ohm's law states the relationship between current and potential difference. And basically states that the voltage across a conductor is directly proportional to the current flowing through it, if all physical conditions and temperature remain constant. and represent mathematically as V=IR. Where V is the voltage across the conductor, I is the current flowing through the conductor and R is the resistance offered by the conductor to the flow of current. And Ohm's law states that the current through a conductor between two points is directly proportional to the voltage between the two points. 

Ohm's law is used to quantify the static values of circuit components such as current levels, supply voltages and voltage drops.