What is the difference between epistemic and deontic modal auxiliary verbs?

A modal auxillary verb is verb such as 'must', 'will', 'should', 'may', 'might' and so on, that indicate something that may or may not happen in a sentence. Whether or not the verb is epistemic or deontic indicates if 'something' will happen or not. For example, the modal auxillary verb 'will' is deontic because it means that the subject of the sentence definitely will happen, whilst the modal auxillary verb 'may' is epistemic because the outcome is less definite.