A linear resistor is a resistor whose resistance does not change with the variation of current flowing through it. In other words, the current is always directly proportional to the voltage applied across it.
Resistors are made from conductors, materials that electricity can travel through easily. As opposed to other types of resistors, linear resistors are effective by making it capable of high power dissipation due to the high surface temperatures generated by it. Resistors act to reduce current flow and lower voltage levels within circuits. Resistors are necessary and play an important role in nearly every modern electronic device.