ZIP archive of roughly 5.6 MB tied to Apple logic board 820-02841. The file name lists only the board number, so the contents are not stated; such packages commonly hold a schematic, a boardview or a firmware dump, and the actual files should be checked after extraction. Apple prints the 820-xxxxx part number on the logic board itself, so match it exactly before using any data here. Boardview content would open in tools like OpenBoardView or FlexBV, while schematics help trace power rails and fault paths.
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 @notebookschematic. Enginerys does not host this file.
How to open a .zip file
Compressed archive that every operating system opens without extra software.