A course is the basic learning entity. If you want to sell a course you need to give it a price (1). If you want to offer a certification for everyone that completes the course you need to setup the type and duration of the certification. The user that creates a course becomes its owner. You can assign more users as instructors for the course. Each instructor may add and modify content according to his user type but not edit the course basic information such as name, category etc.
Note that you can Clone a course and reuse it in another context. When you clone a course its users are reset and the user that clone it become its instructor.
