A voice-over artist can narrate a training video, a commercial message, traffic flow instructions in a GPS system, a story, or how to perform a repair or installation. The VO artist can give a voice to a toy or a character in a computer game. The Voice Over artist can read a short story or a whole book. Many commercial web pages have a choice for the visitor to read or listen to the sales pitch. A Power Point slide show can have a narrator.
Most voices should have friendly, pleasant, positive qualities that attract the listeners. Other extremes are the Voice of God (deep and forbidding), an annoying character, or a negative role model.
There is an old joke about a moonshiner who gave a jug of his whiskey to a friend and he later asked how he liked it. His friend said it was just right. The moonshiner asked what did he mean by just right? His friend said if it were any better, you would not have shared it with me and if it were any worse, it would have killed me. A voice over should not be annoying just as elevator music should not be annoying but also should not be so great that people stay on the elevator to hear the rest of the song.