If you’re publishing a book, you’re going to need a blurb. And if you’re publishing traditionally, you’re also going to need a synopsis.
The blurb is the text on the back of the book, or on the inside of the dust jacket, or on the order page of the retailer. It’s short, and it needs to intrigue the reader without giving much away. No spoilers, just the hook.
The synopsis is the full summary of the book sent to agents when querying. It’s a bit longer, with less hook and more spoilers. Agents need to know what they’d be getting into when they’re reviewing queries before they start requesting partial or full manuscripts from every author with an interesting premise.
If you’ve written a whole novel, chances are you’re pretty attached to a lot of it. So, boiling it down to a couple paragraphs that will grab a reader, or a few pages that might convince an agent to work with you can be tough. How could you possibly pick out just the important parts when it’s all important?
It is all important, but, deep down, you know which parts are the core of the story.