I've been told by several writers that prologues are completely unnecessary in any piece of storytelling. I however, believe they are a very effective way of illuminating integral aspects of backstory.
Prologues can be used to give the story you are telling, some very valuable context.
Prologues are very popularly used in Fantasy or Science Fiction genres, but can also be used in horror, thrillers, or any story which requires a set up of a previous crime or event.
Great post here from StigmataScript about writing good prologues:
Thank you VERY kindly. =)
You’re VERY welcome =)