RAR archive of 920 KB labelled for the ASUS P8H61-M LX board, with an RG suffix whose meaning the name does not explain. Larger than the other P8H61-M LX files, it may contain several documents or a fuller service package, so open it to see what is inside. Files like this are generally used to trace power rails, find test points and compare component values on this Intel H61 desktop board. Check that any included document matches the revision on your PCB 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 @schematicslaptop. 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.