Any time there is a movement there

Any time there is a movement there is resistance. This resistance is useful in electric and electronic circuits. Resistance makes it possible to generate heat, control electron flow, and supply the correct voltage to a device.

Resistance in a conductor depends on four: material, length, cross-sectional area and temperature.
Material: Some materials offer more resistance than others. It depends upon the number of free electrons present in the material.

Length: The longer the wire or conductor, the more resistance it has. Resistance is said to vary directly with the length of the wire.

Cross-sectional area: Resistance varies inversely with the size of the conductor in cross section. In other words, the larger the wire, the smaller the resistance per foot of length.

Temperature: For most materials, the higher the temperature, the higher the resistance. However, there are some exceptions to this in devices known as thermistors. Thermistors change resistance with temperature. They are used in certain types of meters to measure temperature.
Resistance is measured by a unit called Ohm. The Geek letter Ω that is used as the symbol for electrical resistance.
Resistors are devices that provide measured amounts of resistance. They are valuable when it comes to making sure that proper amount of voltage is present in a circuit. They are useful when generating heat.

Resistors are classified as either wirewound or carbon-compostion.
Wirewound resistors are used to provide sufficient opposition to current flow to dissipate power of 5W or more. A watt is a unit of electric power. A watt is equal to one volt times one ampere. Wirewound resistors are made of wire that has controlled resistance per unit length. Resistance causes a voltage drop dissipated as heat and must be eliminated into the air.
Some variable resistors can be varied but can also be adjusted for a particular setting. Resistors are available in various sizes, shape, and wattage ratings.
Carbon-compostion resistors are usually found in electronics devices. They are of low voltage. They are made in 1/8W, 1/4W, 1/2W, and 2W sizes. The physical size determines the wattage ratting or their ability to dissipate heat.