More detailed information on the theory test is available here What is CBT all about?
As a new rider, you are required by law to complete Compulsory Basic Training (CBT) before you can ride on L plates. The Driving Standards Agency syllabus will introduce you to safety equipment and ridering gear, basic machine control, the concepts behind road safety. A qualified instructor will accompany you on a minimum of a two hour road ride. Having reached a safe and proficient level of riding, you will receive a CBT certificate (DL196). This certificate is valid for two years, and allows you to ride displaying L plates unaccompanied on the roadFrom 1st January 1997, all learner motorcyclists must complete CBT before riding on the road.