Archive referencing Apple board 820-1257 and nothing more; the name states no laptop model, revision or type of contents. The roughly 1 MB size suggests a compressed schematic or similar document, but extract it and look before planning a repair around it. Apple prints its 820-series logic board number directly on the PCB, so check that the code matches. A matching document lets you trace power and signal nets, find test points and work out which component is behind a short.
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.