The FTDI board is a USB to Serial (TTL level) converter which allows for a simple way to connect TTL interface devices to USB. The VCC pins of this FTDI cable are configured to operate at 5V or 3.3V I/O just by changing the yellow jumper position.
This FTDI board is based on FTDI original chip FT232RL (datasheet here)
This board has TX and RX LEDs that allow you to actually see serial traffic on the LEDs to verify if the board is working
- 3.3 or 5V output (switchable via Jumpers)