RAR archive for the STI 1091, a system the name links to Malata board 81005, roughly 945 KB. Malata is a Chinese manufacturer that produced boards for other brands, so the number refers to its own design rather than a retail model. The contents are not described, but packages like this usually include schematics or service drawings. Technicians rely on such documents for tracing power circuits and locating components; first verify that the 81005 number printed on the board matches the 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 @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.