Can someone explain me how the Tinkerkit Mosfet Module T010020 works?

Hi all,
I drew the circuit of the whole module on paper including the opamps, the diode and the mosfet but I don’t really get it. It seems to me that M- is on the drain of the (assumigly) NMOSfet. V++ and M+ are connected. So it looks like between M+ and M- is only the diode. How does that work?

Edit: I simply want to short-circuit something with it, is that possible?

It would help immensely if you provide a link or post the schematic you have drawn.

Here how I think it is (DO = Digital Out):

Still not sure what the diode does there, it could be left out I guess? Shouldn't short-circuiting be possible between GND and M-?

Also, shouldn't there be an official schematic of the module since all arduino stuff is open source?

The diode is to protect the circuit from the reverse voltage that a motor produces when power is removed and the magnetic field collapses.

since all arduino stuff is open source?

No all the arduino stuff is not open source. The arduino itself is, but third party stuff is not necessarily open source.