Okay. Very high level, it has some complexities to it, but in a writeoff, you have the intention to collect. You had someone—your supplier—there's been an overpayment and you're looking for your money. For different reasons—the person is deceased, there's bankruptcy or you cannot locate the person who owes you money—you may want to do a writeoff. The writeoff doesn't extinguish the actual debt. If something changes, you may still be able to recover.
For forgiveness and remissions, those are areas where the criteria are for fairness perspective, and for compassionate reasons you may not want to collect something. If you want to remove that from your books, you're going to have to do a remission or forgiveness. In a nutshell, that extinguishes the debt officially.