RAR archive of about 419 KB labelled for the Z97M-PLUS motherboard. The file name says only the model, so the revision and the exact contents, possibly a boardview, a schematic or both, can be checked only after extraction. Boardview files open in viewers such as OpenBoardView and help with locating components and tracing nets, while schematics usually come as PDF. The M in the model name suggests a micro-ATX variant distinct from the full-size Z97-PLUS, so do not mix the two. Compare any revision inside with the PCB marking.
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 @boardview. 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.