RAR archive for the Samsung SM-A310F, the 2016 Galaxy A3, with no further detail about its contents in the name. At 7.73 MB it most likely holds a schematic, service manual pages or troubleshooting guide for this handset. Such material helps a technician trace charging and power rails, find connectors and filters, and diagnose no-power or no-signal faults. Extract it with WinRAR or 7-Zip, and check that the model code and board revision in the documents match the phone being repaired.
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 @Schematic_mobile_iran. 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.