The jumpers of the Slot Connector are used to interconnect the boards of the WiFi Slot form factor. They are included with these modules, but sometimes small parts lost.
At first glance, the PCB square is nothing special. However, the scheme moves power lines and I²C bus from one board to another with nuts and bolts. The result is a strong and reliable connection without soldering, wires, or electrical tape.
To connect, simply twist the platforms together with M3 screws.