"Think of it this way: Sales people are on the front lines, meeting potential clients and closing deals over dinners. Business development reps, on the other hand, are strategizing growth opportunities---that often means working closely with sales to grow business and increase revenue streams (e.g., directing sales people certain to certain industries and markets based on analytics); and it also means working with Product Managers and customers to improve existing products and generate ideas for new features."

(http://www.autoadmit.com/thread.php?thread_id=3457838&forum_id=2#32124449)