A Metronome is a device that produces an audible click or another sound at a regular interval that is set by the user, typically in beats per minute (BPM). Musicians use a metronome to practice playing in time and at a sustained speed.
Metronomes also can include a swinging pendulum or blinking lights that allow the user to keep track of the beats better. In Amsterdam, 1814, an Inventor known as Dietrich Nikolaus Winkel invented what he called 'the Musical Chronometer'.
Johann Maezel then added a scale in 1815 and became known as the inventor of the metronome. He only had a few hundred made which were sent out to friends, and music composers were seeking their feedback, and one of those was Ludwig Van Beethoven who suggested he lower the scale to 40 as the lowest it went was 50.
Musicians find that regular use of a metronome helps to improve their timing and the ability to stick to a tempo. Composers often use a metronome as a standard tempo reference—and may play or sing their work to the metronome to derive beats per minute if they want to indicate that in a composition.