What does cbt mean?

There are quite a few versions of "cbt" these are listed on the link below.

Compulsory Basic Taining. if you take this at the age of 16 with a provisional licence you are entitled to ride a 50cc moped on the road. but you are not allowed to take a pillion passenger, or ride on the motorway and you have to have L plates at all time on the front and rear of your scooter.