RAR archive of 1.10 MB for the N55SF mainboard, with MB meaning motherboard and 2.0 most likely indicating board revision 2.0. The name does not state whether a schematic, boardview or firmware is inside, so extract it to check. For schematics, technicians trace rails and signals; for boardviews, they find parts and test points; for firmware, they reflash the SPI chip with a programmer after saving the original contents. Make sure the revision printed on the PCB is 2.0 before relying on the material.
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.