A potentiometer is a manually adjustable variable resistor with 3 terminals. 
Two of the terminals are connected to the opposite ends of a resistive element, and the third terminal connects to a sliding contact, called a wiper, moving over the resistive element.

Potentiometers are categorized into three main types: rotary, linear, and digital. Rotary potentiometers use a rotating shaft to adjust resistance, linear potentiometers use a sliding mechanism, and digital potentiometers use electronic signals to control resistance

Potentiometers come in two primary types based on how their resistance changes with rotation or slider position: linear and logarithmic (also known as audio taper). Linear potentiometers offer a uniform change in resistance, while logarithmic potentiometers provide a non-linear, exponential, change in resistance.

Potentiometers are also available as mono, dual and multi-gang units. In multi-ganged units, potentiometers are stacked together on the same shaft.