RAR archive of 14.4 MB labelled only with the Samsung model code SM-A750FN, which is the Galaxy A7 2018 variant. The name does not say what is inside, so it may hold firmware, a schematic or service documents; inspect the contents before use. Phone repair files like this are used to trace circuits, locate components or restore software. Check that the exact model suffix matches the handset, because Samsung regional variants differ in hardware and firmware.
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 @SMART_PHONE_SCHEMATICS. 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.
7-ZipWinRARThe Unarchiver (macOS)