RAR archive of 1.30 MB covering Apple board 820-2213. Only the board number appears in the name, so neither revision nor contents are stated; files of this size usually contain schematic pages. Apple marks its logic boards with 820-xxxx part numbers, so read the PCB to make sure it is the same board before using component references. Once extracted, the material supports tracing power rails and data lines, locating test points, and working through a no-power or no-boot fault in a logical order.
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.