Zipped service package for the Xiaomi Mi Mix 2S smartphone, 8.92 MB in size. The name gives only the model, so the exact contents are not stated; archives of this kind usually hold a schematic, a board layout or both. A technician uses such material to follow power rails from the PMIC, locate connectors and test points, and check for shorts on the main board. Extract it and open PDFs in any viewer or layout files in a boardview program. Confirm the board markings match your unit, since regional variants can differ.
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.