A buzzer is an electronic sound-producing device used to generate beeps, tones, or alerts in a circuit. It works by converting electrical energy into sound energy. Buzzers are commonly used as alarm indicators, timers, notification sounds, and user feedback devices in electronics. There are two main types of buzzers: Active Buzzer: Has a built-in oscillator circuit. It produces sound automatically when power (usually DC 3–12V) is applied. It only needs a simple ON/OFF signal, making it easy to use with Arduino or other controllers. Passive Buzzer: Does not have a built-in oscillator. It needs an external signal (like PWM from Arduino) to generate different tones or melodies. Buzzers are found in doorbells, alarms, calculators, toys, appliances, and embedded systems where sound alerts are needed. They are compact, inexpensive, and available in various sizes.