RAR archive of about 61 MB labelled only with the phone model, Motorola Moto G6, so the exact contents are not stated in the name. Given the size, it could hold schematics, layout drawings, service documentation or a firmware package, and you should open it with WinRAR or 7-Zip to see what is inside. Material of this kind is used to trace circuits, locate parts or restore software. Check the exact model variant and board version on your unit before using any document or flashing any image from the archive.
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 @uzb4422. 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.