Boardview for Apple logic board 820-2060, packed in a small RAR archive of about 80 KB. Apple uses the 820-xxxx pattern for logic board part numbers, which is printed on the PCB and must match before you trust the layout. A boardview shows component placement, part designators and net connections, so it is used to locate test points, follow a rail to its source and find a shorted part. Open it with a viewer such as OpenBoardView, FlexBV or a similar tool.
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 @schematicslaptop. 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)