ZIP archive for the Asus ET2220I all-in-one PC, version 1.2 according to the name, most likely the mainboard schematic or related service file. At 193 KB the package is small, so open it to see whether it holds a diagram, a boardview or something else. Make sure the revision printed on the board matches 1.2 before using part references or net names. Service documentation for an all-in-one helps trace the internal power supply input, standby rails, panel backlight and display signals when the unit stays dark or will not boot.
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 @cidschematicandboardviewofficial. Enginerys does not host this file.
How to open a .zip file
Compressed archive that every operating system opens without extra software.