Apple iPhone 8 Plus service pack in a compact 3.33 MB ZIP archive; the name does not specify a board number or what files are enclosed. Expect repair documentation such as schematic diagrams or board layout data that lets you find components, connectors and test pads. Technicians rely on such files to measure power rails, check for shorts to ground and follow charging, display or audio circuits. The Plus model has its own logic board, distinct from the standard iPhone 8, so use these files only on the matching larger device.
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.