At the end of each quiz or exam, you can review the results right away, or you can review them later on.
To review your quiz session,
Go to your dashboard -> Activity -> Select Quizzes or Exams -> Select show sessions in the exam you want to review -> click on view results on the session you want to review.
You will see all the details about the session including Correct/Incorrect Answers, Skipped Questions, Time Spent.
For Quizzes: Select the Answer tab to review each question.
For Exams: Scroll down to the Review Answers section