RAR archive, 92.8 KB, for motherboard 10260-1, a number in the Wistron numbering pattern. The name says nothing about contents, brand or model; the small size points to a boardview or compact data file rather than a PDF schematic. Extract it and check the file type, then open a layout with OpenBoardView or FlexBV to find parts, nets and test points. Verify the board number on the PCB before relying on it for fault finding.
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)