Fixed resistors are made of carbon encased in a plastic cylinder, with a connecting wire on either end. Most resistors used in electrons today are carbon resistors. Older resistors were made of poorly conducting metal, to restrict the flow of the charge.
A resistor will limit the electric current flowing through a circuit and resistance is the curtailment of the flow. Within a resistor, the energy of the electrons that flow through the resistor is charged to heat and light. There are many different types of resistors. They are all made the same with a resistance material encased in a non-conductive material casing, such as plastic, cylinder, with a connecting wire on either end.