A compressed RAR package of about 826 KB for the Xiaomi Mi 5S phone. The name gives only the model, with no document type, board number or revision. At this size it most likely contains schematic or layout pages rather than firmware, but extract it and check. Such material helps a repair technician trace power rails from the PMIC, find components near a short and follow display, camera and USB signal routing. Before trusting the drawings, verify that the board revision printed on the PCB matches 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 @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.