A volume control switch or potentiometer generally comes in three different types: rotary, linear and digital. A rotary potentiometer, also known as a thumb pot, has a wiper that moves along a circular path and can be rotated left or right. A linear potentiometer, also known as a fader or slider, has a wiper that can be adjusted left or right in a straight line. A digital potentiometer doesn't have a wiper and is controlled electronically.
Each type of potentiometer has its own subcategory. For rotary potentiometers, there's the single-turn pot, multi-turn pot, dual-gang pot, concentric pot and servo pot. For linear potentiometers, there's the slide pot, dual-slide pot, multi-turn slide pot and motorized fader. Digital potentiometers an be controlled by up/down signals or protocols like Inter-Integrated Circuit and Serial Peripheral Interface.
In rotary and linear potentiometers, the position of the wiper dictates the device's output voltage. Digital potentiometers, on the other hand, do not have actual wipers, but they have an array of resistive components in series, each equipped with a switch that can serve as a virtual wiper position.
The materials used to make potentiometers include carbon composition, wirewound, conductive plastic and cermet. Carbon composition is the most common material with acceptable noise and wear characteristics. Wirewound is ideal if precision and durability are a requirement. Conductive plastic is expensive but ideal for high resolution and low noise use; that's why it is often found in high-end audio equipment. Cermet potentiometers are ideal when stability and good performance under high temperatures are a must.