Delphi isValidXML usage

I have seen this code here on StackOverflow:

  uses
  Variants,
  Comobj,
  SysUtils;

function IsValidXML(const XmlStr :string;var ErrorMsg:string) : Boolean;
var
  XmlDoc : OleVariant;
begin
  XmlDoc := CreateOleObject('Msxml2.DOMDocument.6.0');
  try
    XmlDoc.Async := False;
    XmlDoc.validateOnParse := True;
    Result:=(XmlDoc.LoadXML(XmlStr)) and (XmlDoc.parseError.errorCode = 0);
    if not Result then
     ErrorMsg:=Format('Error Code : %s  Msg : %s line : %s Character  Position : %s Pos in file : %s',
     [XmlDoc.parseError.errorCode,XmlDoc.parseError.reason,XmlDoc.parseError.Line,XmlDoc.parseError.linepos,XmlDoc.parseError.filepos]);
  finally
    XmlDoc:=Unassigned;
  end;
end;

What would be an example call of these functions ? What is the ErrorMsg ?

Thanks a lot!