Apple schematic PDF of 2.35 MB named simply 5g, which appears to point to an iPhone 5 generation model; the exact device and board revision are not stated, so open the file to confirm. Schematics like this let a technician trace power rails, follow charging, backlight and audio circuits, and find which components hang on a shorted line. The document opens in any PDF viewer. Compare the markings on the logic board with the drawing before trusting component designators or connector pinouts.
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 @Schematics_Mobile. Enginerys does not host this file.
How to open a .pdf file
The standard format for schematics, block diagrams, power-sequence charts and service manuals.