RAR archive for the J1800I-A mini-ITX motherboard, a board with a soldered-on Intel Celeron J1800 as the model name implies. At 192 KB the contents are small, so the package probably holds a boardview or similar repair file, although the name itself does not say. Such data helps locate components, check power rails and identify test points on the compact layout. Open the extracted file in a suitable boardview viewer and make sure the revision printed on the PCB matches before replacing parts based on it.
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.