Buzzer

A buzzer is a tiny loudspeaker. Switch its pin on and off very fast, say 1000 times a second, and you hear a note. The Arduino does that for you with tone: a higher number, a higher note. noTone makes it quiet.

The leg under the + mark to a pin, the other to GND. tone(pin, 1000) sounds until noTone(pin).

More: beeps, notes and the two kinds of buzzer

const int buzzerPin = 8;

void setup() {
  pinMode(buzzerPin, OUTPUT);
}

void loop() {
  tone(buzzerPin, 1000);    // on, 1000 Hz
  delay(60);
  noTone(buzzerPin);        // off
  delay(400);               // the gap: shorter gap, faster beeping
}

A beep is a short tone and a gap. Change the gap and the beeping gets faster or slower; change the number in tone and the note gets higher or lower. The notes of a song are just numbers: 262 is a C, 294 a D, 330 an E, 392 a G, 440 an A.

Two kinds: a passive buzzer (ours) needs tone to make the swings; an active buzzer has the swings built in and sounds as soon as its pin is high, always at the same note. If yours beeps with a plain digitalWrite HIGH, it is an active one; tone works with both kinds.