Small 788 KB rar archive titled OPPO R9, with nothing in the name about the type of document it contains. The size suggests a schematic or a compact service document rather than firmware, but that should be confirmed by extracting it. Such material is used to trace supply lines, locate shorts and follow charging or display circuits on the main board. No hardware revision is stated, so check that designators and layout match the board you are repairing before working from it.
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 @SMART_PHONE_SCHEMATICS. 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.