a piece of music sung or played in the open air, typically by a man at night under the window of his lover.
In music, a serenade is a musical composition and/or performance delivered in honor. Serenades are typically calm, light pieces of music. The term comes from the Italian word serenata, which itself derives from the Latin word serenus.
It provides light to a picture which reaches a sensor by shutter speed. Exposure brings out the light in pictures and is useful when you take a pic that is dark