App note from Vishay on variable resistors primer. Link here (PDF)
A potentiometer is a mechanically actuated variable resistor with three terminals. Two of the terminals are linked to the ends of the resistive element and the third is connected to a mobile contact moving over the resistive track. The output voltage becomes a function of the position of this contact. Potentiometer is advised to be used as a voltage divider.
from Dangerous Prototypes http://ift.tt/2xDwZPV