RAR archive for the Sony motherboard MBX-224, 1.89 MB; the name does not list what is inside, so expect schematic or boardview material that must be extracted first. MBX numbers are Sony internal board designations, while the board itself is usually built by an ODM such as Quanta, Foxconn or Compal. Extract with WinRAR or 7-Zip, then check the contents for the ODM project code and revision. Before relying on the files, confirm that MBX-224 and the revision printed on your PCB match the documents.
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 @alischematics. 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.