Service material for the iPhone 4S, a 3.82 MB RAR archive with no detail in the name about what it holds. Such packages commonly bundle a logic board schematic and boardview layout that help in diagnosing boot loops, no-power faults, charging problems and shorted capacitors on main rails. Use a boardview program like OpenBoardView to locate parts, then measure test points referenced in the schematic. Check the model and board version of the device before relying on the documentation.
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 @schematicslaptop. 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.