What is m2_1 and m2_2 storages?

m2_1 slot   Dan white rabbit slot machine

INSTALL NVMe SSD IN NO OR SINGLE SLOT MOTHERBOARD

Is this OK or should I move the standoff from M2_2 to M2_1 and install the HDD in M2_1? slot but it is not shown in that picture it is The M2_1 slot ist ok, because my crucial P1 is also detected @ every boot So I think this is a SN850 firmware problem or a MSI Bios problem

what are the most popular slot machines in casinos 2 slots will support an NVMe drive The M2_1 slot is of course the best, since it's direct to CPU  So just to be clear , if I use a gen4 M2 nvme on m2_1 slot, it should still allow me