A 361 KB RAR file for the ASUS B85M-K, a budget micro-ATX board with the Intel B85 chipset and LGA1150 socket. No details on the contents appear in the name, so unpack it to find out whether a boardview or schematic is included. Either is useful for finding test points, checking power rails during no-power faults and locating the SPI flash before reflashing it with a programmer. Make sure the revision printed on the PCB matches the document before relying on it.
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 @boardview. 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)