Archive tied to the 3AESV board code, revision 1.2 judging by the RH-12 suffix, packed as a 2.23 MB RAR file. The name gives no device model or content type, so open it with 7-Zip or WinRAR first to see whether it holds a BIOS image, a schematic or a boardview. Separate files exist for revisions 1.0 and 1.1 of the same code, so check the revision printed on your board before using anything inside. Before flashing any image from the package, read and keep the existing chip contents with your programmer.
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.