This is a basic breakout board for the FTDI FT232RL USB to UART/Serial adaptor. The pinout of this board matches with official Arduino and cloned boards but it can also be used for general serial applications. The major difference with this board is that it brings out the DTR pin as opposed to the RTS pin of the FTDI cable.
This board also include a 500mA resettable fuse and a slide switch to select between 5V or 3V3.