Compact RAR archive containing a BVR boardview for the iPhone 5S, with iP5S being a common shorthand for that model. BVR files open in FlexBV and similar viewers, and they show component locations, part names and net connectivity for the phone logic board. That makes it easier to probe lines, find a shorted capacitor, or locate parts during microsoldering. Extract the archive first. The name gives no board number, so check that the layout matches the PCB in front of you.
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 @GENERAL_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.