RAR archive labelled Z87-PRO, a name that matches a desktop motherboard model, though the file name does not say what the archive holds or who made the board. At 331 KB it is small, which suggests a compact boardview, a schematic excerpt or a set of notes rather than a complete firmware image. Open it and check the contents and any embedded board revision before using it. Confirm that the model and revision printed on the PCB match before tracing rails or locating components from this material.
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.