RAR archive of 26.5 MB named only after the board number NM-C661, an LCFC-style number of the kind used on Lenovo boards. An Apple 820-00165 logic board reference is also associated with it in the index. The name does not say what is inside, but its size suggests a schematic, a boardview, or both. LCFC is the Lenovo-Compal joint venture and numbers its boards NM-xxxx. Open the archive and check the board number on each document against the PCB before you trace rails or measure components.
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 @cidschematicandboardviewofficial. 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.