MSI MS-7031 archive in RAR format, 4.80 MB, with nothing in the name beyond the board number. The larger size hints at several files, possibly schematics plus boardview or BIOS data, but that needs confirming after extraction. Technicians use such material to trace power sequencing, locate components and test points, or recover a corrupted BIOS. The MS-7xxx pattern is MSI's own motherboard numbering. Compare the code and revision printed near the slots before working from the files, and back up the BIOS chip before any reflash.
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 @IT_SERVICE_WORLD. 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.