Small 4-digit display including a backback with the necessary electronics pre-assembled and tested to drive the LED segments. Adafruit has created this backpack specifically to minimize the amount of wiring used. Each backpack can get a separate address assigned by setting te 'address jumpers'. This way you can connect up to 8 of these backpacks on a single I2C bus.
The kit comes with a tested LED backpack, a 4-digit 7-segment display and a 4-pin header.
You only need to do a little bit of soldering to solder the display to the backpack. This takes about 5 minutes.
Adafruit has a nice and clear tutorial available for this product.