Ohm's law: According to Ohm's law "At constant temperature, the current flowing through a conductor is directly proportional to the potential difference across its ends."
If I is the current flowing through a conductor and V is the potential difference across its ends, then according to Ohm's law
or V = IR
where R is constant for a given metallic wire at a given temperature, and this constant is named resistance. It is the property of a conductor to resist the flow of charges through it.
If the potential difference across two ends of conductor is 1V and the current through it is 1A, then the resistance of the conductor is 1Ω.