An old name for Issued Currencies on the XRPL. Originally it was an acronym for "I owe you," used to represent a debt or credit relationship between two parties on the XRP Ledger.
An IOU (short for “I Owe You”) is an old name for an issued currency, a digital representation of a debt or obligation between parties within the network. IOUs are commonly used to facilitate the transfer of assets or value without directly involving the native cryptocurrency. They enable participants to create and exchange debt-based tokens, representing real-world or virtual assets, on the XRPL. IOUs serve as placeholders for the actual assets and can be redeemed for their corresponding value. These digital IOUs on the XRPL contribute to enhanced liquidity, efficient cross-border transactions, and broader financial inclusion within the cryptocurrency ecosystem.