MultiMediaCard is an early flash memory card standard. It uses a simple serial interface and lacks the physical write-protect switch found on the later SD cards that largely superseded it. While the removable cards are mostly obsolete, the underlying protocol survives in embedded applications like eMMC, which is widely used for internal storage in mobile devices.
The bootloader is trying to pull the kernel from the MMC interface, but the card isn't initializing.
Related terms
eMMC
An embedded MultiMediaCard provides integrated, non-removable flash storage for compact devices.
RS-MMC
A reduced-size MultiMediaCard is a compact flash memory format designed for early mobile devices.
Memory card
A removable, solid-state storage device used to hold digital data.
Flash memory
An electronic non-volatile computer storage medium that can be electrically erased and reprogrammed.