RAR archive of 655 KB tied to the abit AX78 motherboard, judging by its name. The name does not say what is inside, but packages of this size usually hold a schematic or service documentation for a desktop board. Before probing, confirm that the model and revision printed on the PCB match the documents. Extract it with WinRAR or 7-Zip and look for PDF sheets that help trace power rails, VRM phases and signal paths when diagnosing a no-power or no-POST fault.
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 @cyberlanelectonik. 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)