The FTDI Adapter is a breakout board for the FTD232R serial to USB converter chip. It can be used to add serial communication via USB to any microchip with an UART. It is also used as a programming adapter for Arduino compatible boards that do not have an onboard FTDI chip, such as the Arduino Pro and the Akafugu Serial ISP Adapter.
These files are for use with Eagle CAD.
See here for more details: Akafugu FTDI Adapter.