Questions behaviours determine how questions operate within a given quiz. They can behave in a traditional manner (no results until the quiz is finished), provide multiple tries or even require the student to have a specific level of confidence in their answer.

Core Moodle documentation on Question Behaviours is available on the Moodle WIki, this page just covers the most common scenarios at Strathclyde University

Deferred feedback

This is the most common question behaviour.  The student would answer the question but they will not receive any feedback on the answer until they have submitted the quiz.

Interactive with Multiple Tries

After submitting one answer, and reading the feedback, the student has to click a 'Try again' button before they can try a new response. They can be given hints to help them. Once the student has got the question right, they can no longer change their response. Once the student has got the question wrong too many times, they are just graded wrong (or partially correct) and get shown the feedback and can no longer change their answer. There can be different feedback after each try the student makes. The number of tries the student gets is the number of hints in the question definition plus one.

From https://docs.moodle.org/37/en/Question_behaviours

This question behaviour can be every useful for formative quizzes where you are looking for the student to have opportunities to re-try the questions as they develop their knowledge.

It isn't made clear, but in order to have multiple tries on a question, you must define a set of hints that will be presented to the student on each attempt. The student will get (# hints +1) tries at the question before being given a mark for it.

Manual grading

Used for essay questions (irrespective of what the quiz is set to) but you can now choose to have every question in the quiz manually graded, if you wish.