A more thorough explanation:

IOU (I-oh-yoo) is an abbreviation for "I owe you". It is a written note that acknowledges a debt that someone owes to another person.

For example, if John borrowed $50 from his friend Sarah, he might write her an IOU note that says:

"I, John, owe Sarah $50."

This note serves as a reminder that John owes Sarah money and that he needs to pay her back.

IOUs can also refer to the actual debt itself. In the example above, the IOU is the $50 that John owes to Sarah.

Overall, IOUs are a simple way to keep track of debts between friends or family members.