The gold and silver standards BACKING CURRENCIES were established by central authorities. Meaning, you could convert your USD into an equivalent value of gold.

The gold and silver standards BACKING CURRENCIES were established by central authorities. Meaning, you could convert your USD into an equivalent value of gold. Guaranteed by the US government. And the US government kept an equivalent stockpile of gold in vaults, to reassure everyone that their USD was as good as gold. Then the USD was decoupled from everything. Far before any of that, people actually used gold and silver coins and pieces of coins as currency.