Fixed exchange rate regimes are sometimes implemented through a currency board (Hong Kong) or through dollarization (Ecuador).

Question:

Fixed regimes are sometimes implemented through a currency board (Hong Kong) or through dollarization (Ecuador). What is the difference between the two approaches?
Exchange Rate
The value of one currency for the purpose of conversion to another. Exchange Rate means on any day, for purposes of determining the Dollar Equivalent of any currency other than Dollars, the rate at which such currency may be exchanged into Dollars...