Here's a breakdown:
* Voiceover: This is a general term for any narration or dialogue spoken by a character or narrator that is not part of the scene's action. It can be used to provide background information, thoughts, or commentary.
* Voice-over: This is a specific type of voiceover where the character speaking is not visible on screen.
In the case of hearing a character's voice before their visual introduction, the term "voice-over" is most accurate. It creates an element of mystery and intrigue, allowing the audience to build expectations about the character before they are actually seen.