Many projects need both USB Serial and a single cell Li-ion battery charger. A lot of the serial and charger modules aren't easy to mount in an enclosure. This board can be mounted with the component side up or down. The Tx, Rx, Standby, and Charging LEDs can be soldered to either side of the board. In both of the photos the LEDs are mounted on the opposite side (not visible in the pictures.) The USB connector extends from the side of the board allowing the board to be mounted on slightly curved enclosures. The serial section of the board is powered by USB. When the USB cable is disconnected the serial chip is powered down. Note that your MCU needs to set the TXD and RXD lines to GND to avoid back-feeding power to the serial chip. On Arduino projects you do this by first calling Serial.end() then setting the lines to input, low. You can sense when a new USB connection is made by monitoring the 3v3 line on the board. At that point you call Serial.begin().