Idea: concept, meaning, plan, sense, thought, estimate...
Insight: intuition, understanding of...
Business idea: Business plan, product design, marketing plan, "how to make money" and "what problem will your product solve".
Business insight: Understanding the business, the industry, the current ways - and of course the customer.
To quote Phil Dusenberry of BBDO here talking about great insights when creating advertising:
"That's the power of great insights. Insights, not ideas. There's a difference. Ideas, valuable though they may be, are a dime a dozen in business. Insight is much rarer -- and therefore more precious. In the advertising business, a good idea can inspire a great commercial. But a good insight can fuel a thousand ideas, a thousand commercials."
"Insights are what will let you stay in business, build market share, open new income streams, cement relationships with old customers, and attract new ones."
Buick and the Dodge brothers had some "ideas" when they followed the crowd and added engines to their "coaches".
Henry Ford had an insight when he grasped the "individual transportation for the masses", then acted upon it as he installed the first moving assembly line at his Highland Park plant in 1913, lowering the time-to-produce a T Ford from 70 to 7 hours in half a year enabling "anybody" to purchase a car. His car.
Then he doubled the daily pay and installed a profit sharing scheme - creating a potential customer base as well (especially if it spread to other companies as well - as it would).
Why do VCs (and most other suits) ask a budding entrepreneur "what's your business idea?", "what's the problem you want to solve?" and "what's your business plan?"
They should be asking something along the line of "what's your insight of the industry?" or "What do you understand about the current situation that few (or even nobody) do?"
If you have a good answer to that, a great insight, then you might be in for some interesting times.
If you have an idea - however great - do not stop, keep on searching for the insight.