eMMC (micro)SD card
What is it?
These PCBs contain eMMC storage ICs, which are electrically compatible with SD and microSD interfaces.
They use a different protocol and (depending on the type of eMMC IC used) can be more reliable and faster.
Many (but not all!) SD card slots/readers can also handle eMMC.
These adapters can be used in devices like Raspberry Pis, APUs, etc. to provide stable eMMC storage through the SD slot.