Repair archive for the Apple iPhone 5C, 33.8 MB RAR, with no board number or file list in the name. Likely contents are schematics and boardview files for the logic board. These help with locating components, following signals and finding shorts or missing voltages during diagnosis. Check what the archive contains, open each file with the appropriate PDF or boardview program, and confirm it corresponds to the board you are repairing before relying on it.
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.
7-ZipWinRARThe Unarchiver (macOS)