ASUS X540LJ archive, a 799 KB rar whose RG suffix is not explained in the name, so its exact contents are unclear. The X540LJ is an ASUS 15-inch notebook, and files for it are typically used for board-level repair such as tracing power rails, checking the charging circuit or locating components. Extract it and check whether it holds a schematic, boardview or firmware, then compare the board revision printed on your PCB with the document 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 @SCHEMATICWORLD. 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)