A dial indicator is a precision measuring tool used to measure small distances or variations in height. It features a dial face with a needle that moves in response to a plunger, which contacts the surface being measured. The dial typically displays measurements in either millimeters or inches, allowing users to read the results easily. These instruments are commonly used in machining, engineering, and quality control to ensure parts meet specified tolerances. By providing accurate readings, dial indicators help detect deviations in surfaces, ensuring that components fit together properly and function as intended.