RAR archive of 1.66 MB for Apple logic board 820-2533, with nothing else stated in the name: no model, revision or content list. Apple uses the 820 number as its logic board part number, typically visible on the PCB, so compare it before using the files. The package most likely contains a schematic and possibly a boardview, useful for tracing voltage rails, checking the power-on sequence, locating components and test points, and isolating a shorted line.
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 @Mac_Shematic_Santale. 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.
7-ZipWinRARThe Unarchiver (macOS)