Archive for the Samsung Galaxy A30s, model code SM-A307FN, 1.27 MB in RAR format. The name does not say what is inside; for a file this small it is likely service documentation such as a schematic, layout or component location sheet rather than full stock firmware, but extract it to confirm. Phone repair documents of this kind help locate power ICs, charging circuits and test points during board-level diagnosis. Always verify the exact model suffix, as regional variants of the same phone can differ in hardware.
The button opens the matching file on RM Schematics, or a source page if it is not catalogued there yet. The original attachment is from @esquemaseletricos. Enginerys does not host this file.
How to open a .rar file
Compressed archive — the usual wrapper for a schematic + boardview pair or a BIOS + EC set.