Apple logic board 820-2784 is the only detail stated for this RAR archive of about 1.68 MB. Model, revision and included document types are not indicated, so unpack and inspect it before relying on it. Apple's 820-series numbers appear on the PCB and must match the board under repair. Schematics let a technician trace rails, signals and the power-on sequence, while a boardview shows component placement and test points for faster probing and short hunting.
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)