Small 331 KB RAR archive named R33-MB-B, which looks like a motherboard code with board version B, though brand and contents are not stated. At this size it could hold a BIOS image for a small flash chip, a boardview or a short document, so extract it to see the actual files. Match the code against the marking printed on the PCB before trusting anything inside. If a firmware dump is present, back up the existing chip first and ensure the dump size equals the chip capacity.
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 @schematicslaptop. 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.