A money substitute is a claim to a definite amount of money, redeemable on demand.
Lending is the giving of an asset for a claim on a the promise to pay it back (which is debt).
The return of the asset settles the claims.
Giving credit is lending with the connotation of borrower's trust in that promise.
If the borrower is just a custodian, the claim is a special kind of money substitute called money-certificate or representative money. It does not alter the supply and demand for money.
Reserve ratio = reserved / borrowed.
A custodian is the borrower that keeps the full money amount as reserve. (reserve ratio = 1). If he does not (reserve ratio < 1), he is practicing fractional reserve, which creates money substitutes called near-money that tend to increase the supply / demand relation for money; because now the lender stores value as substitutes instead of as money, while the borrower may exercise his new purchasing power.
*Image: those are Elvis Presley substitutes or near-Elvis Presleys.