RAR archive of 949 KB labelled with the model codes N50A and N51A, most likely a service schematic or board documentation package covering both variants. The name gives no brand, board number or revision, so the contents should be inspected before use. Technicians typically use such packages to trace power rails, follow signal paths and locate components while diagnosing a dead or shorted board. Confirm that the model and board number printed on the PCB match the documents inside, since closely related variants can differ in power circuitry and connector layout.
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 @generalschematics. 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.