Writing for moving images can range from writing feature film scripts to writing adverts to documentary voice-over and more. Writing a voice-over is a great place to start when writing for moving images.
As with all types of creative writing you will need to know your audience and your purpose.
Voice-overs are usually used to inform people. They often accompany short videos, highlighting an important issue. Using still images or motion graphics with a voice-over can be cheaper than making a TV programme or advert. So voice-overs are often important for pressure groups or charities.