Resistance is ability of a material to oppose to the flow of electricity in a circuit. It is used to control the amount of voltage and/or amperage in a circuit.
All conductors offer resistance to the flow of current. The conductors atoms determine this resistance.
Resistance is represented by the letter R. The basic unit of measure is ohm or the symbol.
Good conductors such as silver, copper offer less resistance to the flow of current while bad conductors (good insulators) such as glass and rubber offer more resistance to the flow of current.