Microsoft Lumia 640 archive, 852 KB zip, specifying hardware type RM-1077. Lumia phones kept the Nokia-style RM designations, and each code refers to a particular regional or network variant, so check the label on the handset first. The name does not list the contents; small packages like this usually contain schematic or layout sheets in PDF form. They are useful for following charging and power rails, locating components and test points, and diagnosing shorted capacitors or missing supply voltages on the board.
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.