That's actually a harder question than you might think. There are so many different types of voice-over work. A Voice Actor (aka “Voice Over Artist”, “Voice Over Talent” or just plan “Voice Talent”) is an Actor first and foremost. Voice Actors provide voices in cartoons, television commercials, Radio commercials, Audio Books, TV Promos, Movie Trailers, Replacing dialogue in films, voice over for Industrials, Radio plays, Narration for all sorts of things, Voice Prompts on Telephone Systems, Car Navigation Systems, Video Games, Foreign Film dubbing, Film Looping (background voices), and etc, etc, etc. A Voice Actor can play themselves, or an animal, a monster, an inanimate object (like a toaster). It's the guy on TV who says, “We'll be right back after this!”

There's almost an endless list of what a voice actor can do, and somewhere, right now, there's a voice actor doing it.