Apple logic board package for 820-2997, a 796 KB RAR archive with no model, revision or contents mentioned in the name. The 820-xxxx format is Apple's own board numbering, found silkscreened on the PCB near the edge or under the fan area. Such archives usually contain a schematic PDF and possibly a boardview for programs like OpenBoardView or FlexBV. Check the number and revision letter on your board, then use the files to follow power rails, locate test points and diagnose shorts on the main supply lines.
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.