Polls let you know your audience better.
Determine their involvement and their degree of satisfaction. Ask users to tell more about themselves using leading questions: their positions, interests and hobbies. Also quizzes can be used to gauge how they relate to important world events, how often they use certain goods or services, and why they prefer it.
If you host learning quizzes, find out from your students how difficult the lesson was and what users would like to study in the future. Also, you may easily gauge, in what format it's more convenient for students to learn the material, what time to hold the next lesson, and whether everyone will be able to attend.