In the book Business Made Simple, Donald uses the reference of an airplane to describe a business's components.
Most restaurants focus on the operations, the food and the service, the actual product they are selling. But just because you have an amazing product doesn't mean you are a thriving restaurant.

The engine of your restaurant is marketing and sales—this is what accelerates your business into profitability.

To have a successful restaurant, you need to invest in your engines.

But don't take our word for it; read the book. Donald Miller, Business Made Simple