Knowledge, and the ability to deliberately use that knowledge to control the world around us, is one of the key hallmarks of humanity. Teaching is the art of sharing knowledge. Students acquire knowledge best then they are _interested_ in it, and _comfortable_ with the process. So, a teacher's goal is not just to present the knowledge, but to show why it's useful (interesting) and ensure that the student is comfortable with the process--for instance, knowing it may take effort to learn, but that persistence will lead to success. And, while active learning (learning-by-doing, discovering for oneself) is powerful, it can be inefficient; you don't teach a student how to make fire by leaving them alone in the woods. A teacher should guide and encourage, so that a student really _learns_, but does so efficiently.