Potentiometer structure:
 

A potentiometer is actually a variable resistor, but it is seldom used when a variable resistor is used.
 

The potentiometer has three joints, in the two end with a certain potential difference, different potential sliding contact is in a different position, can cooperate with other components of various circuit, this is its main purpose.
 

There are different resistance and power, such as carbon film and wire winding structure.