In the beginning sections of a story, the first pages or chapters, the writer gives a promise to the reader about the nature of the story that they are about to read. There will be a hint of the genre, the pacing of the story, what the story is about, and the way the story will be told (the narrative construction). In fact, the reader should be fully aware of the nature of the story they are reading by the time they hit the 25% mark (or thereabouts)—ideally earlier. This doesn't mean that they should know 100% what the twists and turns will be, but they should know what the main story is and what sort of experience to expect.
If your story is going to be a high-octane thriller, then there needs to be action in those early scenes. If you are writing a sweet contemporary romance, then we should have met the main characters in this romantic coupling and already be able to see those sparks between the characters—even if they want to kill each other in the beginning. And if your story is going to contain religious or political overtones, then those overtones need to be present early too.
Today, I want to talk about the promises that we make to the reader with the opening pages of our books. It's the promise of the premise.