RAR archive for the MSI Z170-A GAMING PRO desktop motherboard, board number MS-7984 at revision 1.1, most likely holding the schematic set for that board. MS-74xx to MS-7Dxx numbers are the internal codes MSI gives its own desktop boards, and the code is silk-screened near the PCIe slots. Use the diagrams to follow VRM phases, standby rails and the PCH power sequence when a board refuses to start. Confirm the printed revision reads 1.1 before trusting part values, since layouts change between revisions.
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 @IT_SERVICE_WORLD. 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.