voice over

(cinema || television) technique in which an actor reads lines, but is not shown speaking the lines in the video stream. so, for example, we might see martin sheen lying in bed in a decrepit hotel in saigon, and hear his voice say, “saigon… sh-t! i was still in saigon!” but he’s narrating in the past tense, and the martin sheen onscreen is not saying anything. or we might see robert duvall sitting on the beach, and martin sheen’s disembodied voice, calmly recalling, “well, he loved his men… felt safe with them..”

it serves to fill in events in the story that the director doesn’t want to depict on screen; it helps to describe how a character feels about events shown in the scene, or remind viewers that they are currently watching a flashback; it also has been used successfully to explain away absurd holes in the plot that would otherwise ruin the movie.

the voice over (vo) is particularly popular in us cinema and somewhat less so in british and j-panese; non-us movies that are conscious imitating hollywood cliches will usually use it as well.

usually, artistic movies made outside the english-speaking world tend to avoid using the vo because it’s a non-traditional narrative technique, and it looks lazy. a good screenwriter doesn’t need to use it. however, in commercials and tv “journalism” it is almost supernaturally powerful in persuading people of utter nonsense; it’s basically a form of posthypnotic suggestion.
the propaganda effect of commercials is m-ssively enhanced by the use of voice over narration; usually the vo script is a grammatical mess and crammed with logical errors. this actually makes it work as a tool of brainwashing, since the logic cannot be followed by the listener.