there are actually three categories of mistake on driving test, minor major and dangerous actually. (I know cause on my first test I got a tivck on each box).
minor mistakes could be selecting the wrong gear for a given speed or something.
a minor can be something like forgetting to put the hand brake on when you are stopped at a traffic light of junction, (cause then you've failed to secure the car).
that's minor, I did it twice on my first test, so it became a major.
a dangerous fault can be cause by someone else, but basically if you get into a situation that could be dangerous,
on my test some sped past a load of parked cars towards me (parked cars on their side so they should have given way -i was already driving past them), that's a serious fault on my part because of something they did, i mean it's a situation that I couldn't possibly avoid, but even so it's still there.