This DiGrove minishield kit consists of 3 PCBs for the Ports B, C and D of the ATmega328 on your Arduino board. The PCBs allow you to directly connect Grove and DiGrove modules while also duplicating the pins from the Arduino board:
This comes handy for quick experiments with sensors and modules, instead of wiring everything over a breadboard or a dedicated Grove shield you are able to directly connect the modules to the respective ports mini shield.
Note: If you use the Wings for Port B or Port D you still need to feed in positive supply voltage with a jumper wire as 5V and 3.3V supply lines are not available on these pin rows / ports. In case of Port D you also need to connect GND as it is also not available on the underlying pins. See the schematic in the datasheet for more information. The shields have comfortable connectors to feed in both 5V and GND.