We all love a good backstory...

Gotta love that moment when you apply the advice you give to yourself. (more of which later) I'm hot on backstory. So in non-fiction, editors and agents want to know how you're qualified to write the book you want them to publish. They don't always mean, skills and degrees. Your backstory can provide a wealth of stuff that really turns them on and makes them want to champion your book. 

Just for starters in no particular order: why are you writing this book? where did you get the idea?  why do you love the subject or theme? what is the main thing you want your book to do?  for readers? for the world? 

And for fiction writers, the above applies too. Everyone wants to know where a great idea came from. Use the opportunity to share; fascinate and intrigue. Make them want your book.