What does OrderGetString actually return?

 
In the MQL4 Reference guide, it says: "returns the requested property of the order(string)."  However, there are two string arguments for OrderSend right?  The symbol, and the comment.  So which will this return? Both? Either?
 
Erik Volk In the MQL4 Reference guide, it says

Perhaps you should actually read the manual. There is no such function in MT4. List of MQL4 Functions - MQL4 Reference or Trade Functions
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It compiles but does not function

void OnStart()
  {
  OrderSelect(0,SELECT_BY_POS);
  PrintFormat("<%s>", OrderGetString(ORDER_COMMENT) );

2021.09.30 11:12:44.352    testscr EURSGD,Daily: <(null)>

Erik Volk: So which will this return? Both? Either?

In MT5, read the manual: OrderGetStringENUM_ORDER_PROPERTY_STRING