RAR archive of 7.55 MB for the Samsung SM-A310F, the Galaxy A3 2016 model. The name states nothing about the contents, which for Samsung packs commonly include schematic pages and sometimes a component layout. Use it to trace PMIC outputs, battery and charging lines, the display connector and sensor circuits, and to find test points when diagnosing no-power or no-charge faults. A RAR extractor such as 7-Zip or WinRAR opens it; check that your board revision printed near the connectors matches the drawings before relying on them.
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 @tamirat_moobile. 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.