Samsung Galaxy J8 archive for model SM-J810F, 2.68 MB in RAR format. The name does not specify the contents; given the size it is likely a schematic, service document, or small firmware component rather than a complete ROM. Extract it with WinRAR or 7-Zip to check what is included. For phone repair such material helps locate components, trace power and charging lines, or restore a partition, but always confirm the exact model code on the device label before use.
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 @esquemaseletricos. 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.