Corrective actions are what you do to fix a problem. These include both immediate actions to 'put out the fire' and also the longer term measures you take to ensure the problem won't occur again.
Corrective actions are reactive - something has gone wrong and these are the actions taken to deal with the problem. Non-conformances are resolved through corrective actions.
This will include the immediate corrective actions you take to keep your customer happy, e.g. you sent the wrong part and will immediately replace it with the correct part.
However, 'dealing with it' for ISO 9001 means that you eliminate the problem AND make sure it will not happen again, so the corrective actions you take will also include the longer term actions you take to make sure the problem will not occur again.
The problem might be identified in processes, materials, suppliers, the product, the service, the workplace, or the management system itself.
You might find opportunities for corrective actions through:
ISO 9001:2015 no longer requires a documented procedure for Corrective Action but you must still "retain documented information" i.e. keep records of what went wrong and how you corrected it.
You'll need to establish the steps that will be taken to:
Records of your corrective actions provide evidence that the problem was recognised, corrected, and proper controls installed to make sure that it does not happen again.