A potentiometer is a three-terminal resistor with a sliding or rotating contact that forms an adjustable voltage divider. If only two terminals are used, one end and the wiper, it acts as a variable resistor or rheostat. — The measuring instrument called a potentiometer is essentially a voltage …
A typical single-turn potentiometer
Single-turn potentiometer with metal casing removed to expose wiper contacts and resistive track
PCB mount trimmer potentiometers, or "trimpots", intended for infrequent adjustment
Size scaled 10k and 100k pots that combine traditional mountings and knob shafts with newer and smaller electrical assemblies. Note the "B" designating a linear taper.