The possible order types for an option order are:

• Buy to open: a buy order to open is to initiate a new option position
• Buy to close covered: a buy order to close a previously written sell to open covered or sell to open uncovered option position with an underlying security or option
• Buy to close uncovered: a buy order to close a previously written sell to open covered or sell to open uncovered option position without an underlying security or option
• Sell to close: a sell order to close a previously opened buy to open position
• Sell to open covered: a sell order to write an initial option position with an underlying security or option
• Sell to open uncovered Puts: a sell order to write an initial Put option position without an underlying security or option