Central Bank Activities
A central bank, reserve bank, or monetary authority is the entity responsible for the monetary policy of a country or of a group of member states. It is a bank that can lend money to other banks in times of need. Its primary responsibility is to maintain the stability of the national currency and money supply, but more active duties include controlling subsidized-loan interest rates, and acting as a lender of last resort to the banking sector during times of financial crisis (private banks often being integral to the national financial system). It may also have supervisory powers, to ensure that banks and other financial institutions do not behave recklessly or fraudulently.
Intervention
Official intervention in the foreign exchange market means that the central bank or other agent of the government buys or sells foreign currency in an attempt to influence the exchange rate value. Purchases of foreign exchange usually are intended to push down the home currency value of the exchange rate, and sales usually are intended to push it up.
Sterilized Intervention
In a sterilized intervention, the central bank offsets the purchase or sale of foreign exchange by selling or purchasing domestic securities so as to keep the domestic interest rate at its target. Since the domestic interest rate usually is considered the main determinant of the value of the domestic currency, many argue, it must change in order to influence the exchange rate. Sterilized intervention may be especially useful when the exchange rate is under speculative attack (that is, when a change in the exchange rate is not justified by fundamentals) or to help coordinate private sector expectations