Correcting...

If there's something wrong, what should we do? From ISO9001:2008 point of view, you need to correct the situation. First, you need corrections. Corrections are immediate actions. Some say it containment actions.
Say you have toothache. Your correction will be to extract the tooth (could be painful).

After you have taken the immediate action, so what's next? Don't you think you need to avoid the same thing from happening in future? Therefore, you need to take corrective action. An action which is taken in order to prevent recurrence. Having extracted the tooth earlier, what kind of action you need to take to prevent the next tooth or teethache. You extract all your teeth. No, that's too extreme. Probably a checkup to make sure no more cavity or hole in any teeth. If yes, maybe a filling will do. (Note: This is of course assuming the root cause is due to tooth cavity)

OK, you have ensure all of your teeth are in good condition. What's next? Don't you think you need to take precaution? Therefore, you need to take preventive action. An action taken to eliminate the causes of potential nonconformities in order to prevent their occurrence. In other word, take action to keep your teeth healthy and avoid your teeth from developing any cavity. You can brush your teeth regularly, reduce eating sweet or chocolate or anything which can prevent teeth cavity.

So in any wrong doing or nonconformity, take correction, corrective action and preventive action. You are then on path for ISO certification.