I used a very plain example before, and I'll use it again.
We'll take a taxi company, for instance; we don't regulate taxis, but it's a good example. We might have a regulation that says your brake pads have to be five millimetres. So we come in once a year as the regulator and we take off the tire and we look at that tire to see whether or not the brake pad was less than five millimetres. If it were less, then we might slap a fine on you or something like that. All that tells us is that at that particular time, that one time of year, the brake pad was the required thickness.
With the safety management system, we would say that you have to have a system in place to ensure that the width of your brake pads is being continually looked at and to ensure that the person looking at them has the required qualifications to do so, and you have to document that. So we would go in then and take a look at the system they have in place to ensure, on a daily basis, that they are indeed meeting the requirements of the regulation.
Obviously, when we're talking about civil aviation, it's much more complex than that, but in the short time I have available, I think that's a quick explanation of how it works.