For Apple board 820-2510 this RAR archive, about 2.26 MB, collects repair documentation whose exact contents are not specified by the name. No model, revision or file list is given, so the first step is extracting it and identifying a schematic PDF or boardview file. With a schematic you can follow power rails and enable signals; a boardview opened in OpenBoardView or similar shows component positions and test points. The 820 number is Apple's own logic board part number, and it should match the marking on your PCB.
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.