Currency is physical tokens of value for trading money. Money is a system that fulfills several criteria: unit of account, medium of exchange and store of value. Not debt in any meaningful sense, apart from systems that lack trust for store of value or stability for unit of account, in which case explicitly linking to another less easily gamed asset is supposed to increase trust.

Debt can be money if the legal system is sound. But money doesn't need to be debt if the money issuer is trusted not to debase the currency.