There are two types of questions that you will come across when watching a tutorial: Quizzes and tests.
Quizzes are asked at the end of every lesson and consist of a single question based on the lesson that you just watched. If you get the quiz correct, you won't be asked the question again. If you don't get the quiz correct, you might be asked the question again either as a part of the same quiz at the end of re-watching the same lesson or during a test. Quizzes do not have certificates and you do not have to pass all of the quizzes for a course to be able to take the final test.
Tests are a collection of questions that are asked at the end of watching an entire course and cover all of the topics that were covered throughout the course. The number of questions on a test will vary depending on the length of the course that you just watched. Once you pass a test, you can download your certificate to show off that you not only have watched a specific tutorial but you actually understand the techniques that were taught in the tutorial.