Boardview for the ASUS CS-B desktop motherboard, revision 1.03C, contained in a 132 KB RAR archive. A 1.03B layout of the same board exists too, so match the exact revision letter on the PCB. In a boardview program such as OpenBoardView or FlexBV, the file reveals component outlines, net names and pin connectivity, which helps trace power rails from the VRM, locate test points and find the source of a short without guessing.
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.
7-ZipWinRARThe Unarchiver (macOS)