Small 141 KB RAR archive named after KMRX1000BM-B614, which appears to be a memory chip part number, followed by BGA221, most likely the package ball count. The name does not say what the archive contains, so treat it as a reference or dump set for that component and check the contents before use. Files like this usually hold a firmware or data image, or pinout notes, for a BGA memory read with a socket adapter on a programmer. Verify the marking on the actual chip matches and save the original data before writing.
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 @emmcufsdumps. 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.