This is only the PCB for the MaxSerial. If you're ordering a kit, this is already included, but we sell them separately here.
The MaxSerial is an Arduino Diecimila like board which connects to a regular serial port. Unlike many others, the MaxSerial uses an industry standard MAX232 chip to ensure reliable communication. If you want the USB Diecimila ease of use and reliability but without the USB, this is your best bet.
You'll want to peruse the directions for more details and a complete part list.