It's a common question at technology companies: What is business development? I'm still something of a beginner in this profession but I'm nevertheless prepared to give one answer.
Business development is business engineering; it's using business machinery and relationships to make your company more efficient, faster, more beautiful, etc. It's a fundamentally creative exercise ("What if we...?") that requires a fundamental understanding of your business and business model.
Where are the moving parts?
As business engineers it's important to understand the "simple machines" of your business. Where are the ramps that can be made frictionless? Where are the levers that can be made longer? Where are the wedges that can be used to open up a new opportunity? Which of these simple machines can be combined to create something more sophisticated and effective?
Only when you understand your machine can you start thinking about ways to improve it.
One question I often ask candidates for business roles is to describe the business machinery of their current or previous companies. I ask them not to describe the enormous opportunity or pitch the product but to tell me at an abstract level how the machinery worked. If they can only see the product and the vision (both very important things) and not the machine itself then I know it's a bad fit.