Xiaomi M3 archive, 14.4 MB in ZIP format, whose name gives only the model designation and no indication of whether it contains schematics, layout drawings or firmware. The label most likely refers to the Mi 3 handset, but that should be confirmed from the contents. After extraction, schematic or layout files can be used to trace power rails, locate test points and connectors, and diagnose shorts or missing voltages. Check which viewer the files need and verify that the board markings on your phone match the documentation 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 @esquematicosparatodos. Enginerys does not host this file.
How to open a .zip file
Compressed archive that every operating system opens without extra software.