Your examiner will ask you two vehicle safety questions, these are also known as the ‘Show me, Tell me’ questions. The examiner will ask you one ‘Tell me’ question at the start of the test and one ‘Show me’ question whilst you're driving. These questions are from a bank of questions which your driving instructor will have worked through with you throughout your training.
These questions shouldn't cause you any problems. So just take your time to make sure you cover the answers fully. The emphasis being - take your time.
At the start of your test, your nerves will settle much quicker if you take your time to deal with the ‘Tell me’ question properly, just like you have been doing on your lessons.