Archive labelled Z87-K, corresponding to an entry-level Intel Z87 desktop motherboard name used by Asus; the file name carries no revision or description of the contents. With about 500 KB of data it most likely contains board layout or service documentation. Extract it and check the format, since boardview data is opened in dedicated viewers and helps locate components, measure test points and follow nets when tracking a short. Make sure the board revision matches before trusting the layout.
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.