These are questions that you will be asked during your practical test. One Tell Me question will be asked before you set off out of the test centre. This question is what it says on the tin. You are just required to tell the examiner the answer, not operate anything. Then during your drive, you will be asked to show the examiner how to operate one of the cars controls. The list of what could be asked is within the link below. You will not fail your test if you answer any of these incorrectly, but you will receive a driving fault. You must of course be confident about operating the controls safely without losing control of the car. Your instructor will also go through these with you. But it will give you a head start to learn at least the generic questions beforehand.