MSI service material for the MS-12221 mainboard, packed as a 1.15 MB RAR archive, with PR210 appearing in the name, most likely the laptop model the board belongs to. MS-xxxx numbers are MSI own board codes, and the trailing digit usually marks a variant of the base MS-1222 design. Inside is likely a schematic or boardview set for following power rails, identifying MOSFETs and controllers, and finding test points. Check that the exact MS-12221 marking and revision on the PCB match before working from 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 @generalschematics. Enginerys does not host this file.
How to open a .rar file
Compressed archive — the usual wrapper for a schematic + boardview pair or a BIOS + EC set.