Compact ZIP archive of 1.02 MB labelled for the Apple iPhone 5S. The name gives no board number or file list, so open the archive to find out whether it contains a schematic, boardview or other reference material. Documents like these are used to trace circuits, find the position of a given component or test pad and compare measured voltages against the design. Check that the logic board matches the 5S, as the 5 and 5C look similar but use different boards, before relying on any value.
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 @esquematicosparatodos. Enginerys does not host this file.
How to open a .zip file
Compressed archive that every operating system opens without extra software.