BVR boardview archive labelled iP5C, most likely covering the iPhone 5C logic board, compressed as a 57.3 KB RAR. Once extracted it can be loaded in a boardview viewer that reads BVR, such as OpenBoardView, to show component outlines, pin names and nets. Technicians use this kind of file to locate capacitors, connectors and test pads, follow a signal between chips, and measure diode values against known nets. Check that your phone variant matches before relying on the layout.
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.