Corrective and preventive action are two ways of helping to make sure that things are working the way they should in a company or organization.
Corrective action is when something has already gone wrong and someone needs to fix it. For example, if you have an item in your warehouse that you shipped to a customer that is wrong, you would take corrective action to make sure the right item is sent to the customer.
Preventive action is when you do something ahead of time to make sure something goes wrong in the first place. For example, if you think that a certain process could cause a mistake, you can set up preventive action to make sure that it doesn't happen. This could include something like checking the items before they are shipped out or training employees on how to do the process correctly.