I apologize for the delay in responding, and thank you for posting. Director's notes, sometimes called a director's statement, explain why you want to make the film and how you'll tell it. A common structure: why this story matters to you, the tone and themes, the visual approach (look, camera, color, references), how you'll work with actors, and how you'll make it on the budget.
Keep it to one or two pages and make it personal. Funders want to see your vision and that you can deliver. Our Directing forum is a good place to share a draft for feedback.