Quizzes can be assigned to you as stand-alone quizzes, or as part of a course. Quizzes are used by admins to test a learner's knowledge and find out which areas learners need to be trained further in.
To complete a quiz, navigate to your assignment email and click Start quiz.
To start a quiz from the learning area, go to Learn, find the quiz and click Start.
To complete a quiz, simply answer all of the questions presented to you until you've answered all of the questions.
At the end of each quiz, the results are sent to your admin. You can redo the quiz, but unless the quiz is re-assigned to you, only the results from the first attempt will be taken into account.