Apple logic board 820-3208 revision A files, compressed into a 1.75 MB zip. Only the board number and revision appear in the name, without a model. Contents are likely the schematic and maybe a boardview for that board, handy for following signal paths, measuring rails, checking diode-mode readings and locating specific parts. Extract and open schematics with a PDF reader, boardview files with OpenBoardView or similar. Always check that the 820 number and revision silkscreened on the board are the same before use.
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.