Compressed RAR package of 1.90 MB named after the code 3CESL-RH-01, likely a motherboard identifier with revision RH-01, though no brand, model or content type is given in the name. Open it with 7-Zip or WinRAR to see whether it holds a BIOS image, a schematic or a boardview. Before relying on any of it, confirm that the number and revision silkscreened on the PCB match. For a flash dump, read and save the existing chip with a programmer before writing anything new.
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.