It's a USBtinyISP AVR programmer. You can use it to upload sketches using ISP header, burn a bootloader to Arduino, set fuses, etc... It has the following improvements:

• dual USB input: programmer can be plugged directly to the USB port, no hassle looking for a USB cable or it can be connected using mini USB cable (not included) if you need to work farther from USB port.
• variable output voltage: It has 3.3V and 2.7V 80mA voltage regulators on board. You can select output voltage from 5V, 3.3V, 2.7V or external using the slide switch. The selected voltage is indicated using colored LEDs.
• dual ICSP connectors: Programmer has both male and female ICSP connector. It can be plugged directly to the ICSP header on the device you are programming without a need for the ICPS cable. You can still use the cable with the male header as usually (cable is optional). Pin 1 on the female header is marked by a dot, near pin 1 of the male header.
• status LEDs: It has four status LEDs: USB (green) - it has been recognized by PC; PWR (orange) - it is powered (when voltage selector is in the EXT position the programming device must provide power); PRG (red) - it is programming; DTA (blue) activity on MISO, blinks during programming
• MISO LED: this LED blinks during programming, you can also control it from the device you are programming, you can use it as a debug LED similar to the LED on pin 13 on Arduino.
• ATTiny sockets: Plug ATTiny85 or ATTiny84 directly to the programmer, no need of messy wiring on the breadboard, simply plug and play. New to ATTiny? Then make your first program to blink the MISO LED!
• small form factor: all of this cool features stuffed in a space of an USB flash drive.

Drivers: get drivers from here