This dongle connects to a PC and allows data such as BLOCKLY code to be downloaded to the SnapCPU.
Your kit may have the original blue or new red dongle - both work exactly the same, they just connect a little differently.
By utilising a direct cable connection, students know exactly which kit they are coding for.
The also allows data to be reported back to the PC and provides power to the project circuit. The power is limited by what the PC can provide through the USB port, so for power hungry circuits such as those using multiple motors or other high power devices, the use of the battery box is recommended.