This tiny breakout board is used for serial connections over USB (eg. Arduino programming). It's pinout matches that of the FTDI cable for official and cloned 5V Arduino boards. The chipset used it similar to the popular FTDI - the Prolific CP2102.
The major difference with this board is that it brings out the DTR pin as opposed to the RTS pin of the FTDI cable. The DTR pin allows an Arduino target to auto-reset when a new Sketch is downloaded. This is a really nice feature to have and allows a sketch to be downloaded without having to hit the reset button. This board will auto reset any Arduino board that has the reset pin brought out to a 6-pin connector.
If you want to configure your MinimOSD or AfroMini Amaze firmware then you will need one of these adapters.
Can also work at 3.3V, on the voltage pads on the rear of the board cut the link between the 5V and centre pad, add in a solder jumper between centre and 3.3V pad. Check the output voltage with a multimeter.