What is difference between marketing , sales and business development?

They're all interrelated but different: Sales is where the rubber meets the road - creating that sense of urgency to purchase, matching customer need to company's product /solution, and getting dollars in the door. Marketing is various methods (usually involving spending money) to gain sales, which includes paid advertising (direct mail yellowpages, TV, radio, internet, Goodyear blimp, park bench signs, etc), free advertising, community involvement, branding, search engine optimization. But also involves picking up cigarette butts in your parking lot, making sure the waiting room is clean, buying a walnut reception desk - anything that promotes an image of you and your company to the public. Business development includes sales and marketing but much, much more... strategic alliances, research and development of new products, market analysis, basically the big idea and future plan.

Marketing is the process of identifying the needs, wants and expectations of your consumers whether potential or actual. Sales, is the application of your marketing results in order for the company to serve the market with their product. If your marketing effort and sales effort suceeds, then you have business development.

Calisoxfan has hit it on the nose. Well put. Vote for him for best answer:-)