Revision A files for Apple logic board 820-2838, compressed into a 1.29 MB zip, with no model stated in the name. The archive likely holds a schematic and possibly a boardview specific to this revision. Technicians use such documents to trace power sequencing, measure rails, locate components and test points and isolate shorted parts. Schematics open in any PDF viewer and boardviews in OpenBoardView or FlexBV. Since other revisions of 820-2838 exist, confirm the revision letter printed on the PCB 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.