What does tremelo mean in music?

In music, tremolo is an effect created by rapidly alternating one note. The purpose of a tremolo effect is to provide an ethereal feel, and also, create a shimmering texture or a tremulous sound which gives an expressive sound effect.

Tremolo effects are widely used across both orchestral, classical music pieces like string instruments of a full orchestra and popular music like a guitar amplifier with its tremolo pedal or knob setting used for tremolo effects on electric guitars during their individual sections within songs.