Archive named A510FD, the model code of the Samsung Galaxy A5 (2016) dual-SIM variant, SM-A510FD. The file name does not say what is inside. At 1.54 MB it most likely holds a schematic, a troubleshooting guide or a small set of repair documents rather than a full firmware package. Extract it with WinRAR or 7-Zip and look at the contents first. Then confirm the model and hardware revision of the phone match before using any component positions or measurement values from 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 @mobile_jump2. 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.