During your driving test you will be assessed and marked on an iPad. The examiner used to use paper and that sheet is below. This sheet is very similar to what is used on the iPad today apart from some of the reverse exercises have changed (more info here).
You're allowed no more than fifteen driving faults (often referred to as minor faults) and no serious or dangerous faults.
The examiner will mark driving faults in the wider boxes, serious faults are marked in the column below 'S' and any dangerous faults in the column below 'D'.
If you persistently keep getting the same driving fault in a particular category (for example box 19 Following distance) then the next fault will be serious, which would result in a fail.