How would an economist categorize exchange rate systems? How would the IMF make this classification? In what

Question:

How would an economist categorize systems? How would the IMF make this classification? In what ways are these same? How are they different?
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...