Voice Over is a technique used where sound is used on radio, film making, television, theatre or other types of presentations. Usually used in advertising and documentary scenarios, it is separate from the narratives or in-person actions.
It is usually pre-recorded. It has been used since the early days of radio, this technique is used in most commercial television advertisements. For more information about voice over artists, visit this website.
While in the days passed, before the advent of voice recording, the actor would provide live spoken ads on the radio, and also act through their voices for the purpose of radio entertainment. This can be used in several ways:
Translation: An alternative to subtitles or dubbing, some countries use sound for language localisation. Worldwide, news and documentaries will use this technique as a method of translation if necessary.
Character device: Cartoons may be the most common character, we know where our words are used first and foremost. There are several very versatile voice actors who can provide various varying sounds for all types of characters.
Creative devices: In fiction, characters can reflect their situation or their past, or someone who observes stories can provide narratives from outside the action. This gives the effect of the omniscient character that guides viewers through the story.