Small 100 KB RAR archive named for the A78M-E board with what appears to be revision 1.03A; the name does not state the brand or what kind of document is inside. The contents could be a boardview, schematic or firmware, so open the archive and inspect the file extensions first. If it holds a boardview, a viewer such as OpenBoardView will show component placement and nets for tracing faults. Match the board model and revision printed on the PCB against the archive name before using any data from 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.