Prologues can serve a variety of purposes. They can also be ‘teasers’ of the main action, even a ‘teaser’ of the ending (I’ll write more about that later) or even a way to set up a red herring to fool the audience into following the wrong lead. If it’s a crime novel, it could be the last moments of a murder victim. If it’s a fantasy or sci-fi, it can get all the exposition out of the way in one go so the main story isn’t encumbered with it (just think Star Wars).
But, are they really necessary?
Is using it an exposition an admission of lazy writing?
Does using it as a teaser make it feel too much like television?
Is misleading the readers from the start unfair to them? Are they so used to it that they’re not misled anyway?
Are they more suitable in some books more than others?
Let me know in the comments below.