It's a small USB to TTL serial tool, using the PL2303 chip.
You can use it to connect some serial device to your PC via USB port, an avr, an msp430 or an stm32 for example.
It's very cheap compared to the ft232 alternative and works very well, up to more than 1mbit/s.
The DS18B20+ is a programmable resolution 1-wire digital thermometer in 3 pin TO-92 package. This digital thermometer provides 9bit to 12bit celsius temperature measurements and has an alarm function with non-volatile user programmable upper and lower trigger points. The DS18B20 communicates over a 1-wire bus that by definition requires only one data line...