is a popular retro gaming operating system designed specifically for Amlogic -based TV boxes and handhelds. The specific file EmuELEC-Amlogic.arm-3.9-Generic.img.gz (often abbreviated in user queries as "arm39genericimggz") is the legacy 32-bit image used for older S905, S905X, and S912 processors.
To make this file "work," you can't just copy it to an SD card. It requires a specific flashing and configuration process: emuelecamlogicngarm39genericimggz work