RAR archive of 1.33 MB for the Apple iPhone 4s, with no further information in the name. Packs of this size usually carry a schematic or boardview, but extract it to check. A RAR file opens with tools such as WinRAR or 7-Zip. The documentation helps locate components, trace rails and signals and check suspect lines for shorts on this older logic board. The iPhone 4 and 4s boards differ, so make sure the device is a 4s before using the reference material for measurements.
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 .rar file
Compressed archive — the usual wrapper for a schematic + boardview pair or a BIOS + EC set.