RAR archive for the X450LD laptop mainboard, revision 2.1, around 1.12 MB. The name does not reveal the contents, so extract it with 7-Zip or WinRAR to see whether a schematic, a boardview or both are inside. Such material lets a technician trace power rails, locate MOSFETs, coils and test points, and narrow down shorted or failed components. Separate packages for revisions 1.1 and 2.0 of the same model also exist, so read the revision silkscreen on the PCB and use the one that matches.
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.