A potentiometer is basically a voltage divider used for measuring electric potential (voltage). This is done by balancing it against the potential difference produced by passing a known current through a known variable resistance.

A rheostat is an adjustable resistor used in applications that require the adjustment of current, or the varying of resistance in an electric circuit. The rheostat can adjust generator characteristics, dim lights, and start or control the speed of motors.

Resistor trimmers generally are in the form of a potentiometer (pot), often called a trimpot. Potentiometers have three terminals, but can be used as a normal two-terminal resistor. Trimpot is a registered trademark of Bourns, Inc. and the device was patented by Marlan Bourns in 1952. The term has since become generic.