Compressed package, 1.24 MB, named 3D1 with the number 20, which may be a revision indicator. Beyond that the name is uninformative, so the type of material inside, schematic, layout or dump, can only be identified after unpacking with WinRAR or 7-Zip. Material of this kind is used to locate components, read test points and follow power rails while diagnosing a fault. Make sure the board under repair carries the same marking before relying on the reference.
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 @cyberlanelectonik. 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.
7-ZipWinRARThe Unarchiver (macOS)