Answer:
US currency has value backed by the federal government.
Step-by-step explanation:
This is what the phrase means. The US currency is not backed by silver or gold. Instead, it is backed by the faith that people put on its legality, and by the approval of the federal government. The federal government backs US currency, and in this way, ensures that people will fully accept its use. This is why it can be used as "legal tender" for all debts, public and private.