The difference between business development and sales
Business Development and Sales is about working with external parties. Business development is about working with partners to sell to customers. For example, you look for distributors who are willing to sell the products for you. Where in sales, you sell directly to the end customer. For courses, business development involved recruiting portals, training institutions, etc to sell the courses for you. For sales, it involves selling to the participants directly or through the training manager of the company.
Check out this link for a more detailed explanation http://andrewdumont.me/the-difference-between-sales-and-business-development/