Boardview file in BRD format for the Apple logic board 820-2838, compressed to only 72 KB; no revision or model is stated in the name. BRD layouts open in viewers like OpenBoardView or FlexBV and let a technician search parts and nets, see which components share a rail and find test points while chasing a short. Apple's 820-xxxx numbers identify specific logic boards, and revision letters can move parts, so check the full marking on your PCB before probing by location.
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.