Checking for prior knowledge
Often instructors will teach a course not knowing what it is the students already know. If you don't ask questions that refer to prior knowledge students easily get lost in the current objective.
I couldn't agree more. For example, I teach pharmacology and pathology. A lot of the material in the textbooks is basically a review of anatomy, which is a course the students have already taken or take concurrently with my courses. It's always good to see how much of a grasp they have on that material. It allows me to gauge how much class time I need to devote to "reviewing" this material before moving on to new things.
I agree. Some students are very enthusiastic about a topic and will do a lot of research on their own. Others may have some real world experience and then there are those who are novices. I find it important to ask questions that allow me to gage where everyone's level of knowledge and skills are. This helps me better prepare for the class as a whole and reaching certain individuals to bring them up to speed.
