Compressed RAR package for the K43L notebook, with 3.1 in the name most likely marking the mainboard revision. The file name does not list the contents, so unpack it with 7-Zip or WinRAR to find whether a schematic, boardview or both are included. Such documentation is used for diagnosing no-power faults, tracing voltage rails and locating components on the board. Compare the revision silk-screened on the PCB with 3.1 before relying on component designators, since layouts and values may differ between board versions.
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 @alischematics. 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.