Repair package for Apple logic board 820-3023, delivered as a 1.38 MB RAR archive. The file name offers only the board number, with no revision, model or listing of included documents. Such archives usually bundle a schematic and sometimes a boardview for diagnosing a dead board, tracing voltage rails, finding a short to ground or identifying missing components. Apple boards carry the 820 number near the edge of the PCB; verify it matches, and note that a different revision may change part placement and values.
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.