uses
  uHelper, System.SysUtils, Winapi.Windows, Winapi.ShellAPI;

// ...

function GetFileTypeDescription(const AFileName: String): String;
begin
  var AShFileInfo: TSHFileInfoW;

  ZeroMemory(@AShFileInfo, SizeOf(TSHFileInfoW));

  var AFlags := SHGFI_TYPENAME or SHGFI_USEFILEATTRIBUTES;
  if SHGetFileInfoW(PWideChar(AFileName), 0, AShFileInfo, SizeOf(TSHFileInfoW), AFlags) <> 0 then
    result := AShFileInfo.szTypeName
  else
    result := '';
end;

// ...

begin
  try
    WriteLn(GetFileTypeDescription('C:\Windows\Regedit.exe'));
    WriteLn(GetFileTypeDescription('.txt'));
    WriteLn(GetFileTypeDescription('.pdf'));
  except
    on e : Exception do
      WriteLn(e.Message);
  end;

// ...

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