Small RAR archive, 1.06 MB, carrying service manual documentation for a model coded MS82; the file name provides no manufacturer, revision or product category. Given the size it probably holds one or two PDF documents, such as a circuit diagram and a basic service guide. Material like this supports tracing supply voltages, identifying components and checking a shorted line before replacing parts. Unpack it with a standard archiver and compare the code on the device or its board with what the documents state before using the values.
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 @pdf_servicemanual. 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.