Small RAR archive, about 98 KB, tied to the ASUS X1403ZA laptop with Rev21 in the name, likely referring to a board revision 2.1. The name does not state what the archive holds, so it could be a boardview, a schematic excerpt or another service file; inspect the contents after extraction before relying on it. For repair work, match the revision printed on the mainboard to 2.1 and use whatever viewer suits the enclosed format, whether a PDF reader for diagrams or a boardview program for layout files.
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 @Boardviewno. 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.