RAR archive named s21, 5.04 MB, with no brand or details stated; it most likely relates to a Samsung Galaxy S21, but the name alone does not confirm which variant or what files are included. Extract with WinRAR or 7-Zip and check whether it holds schematics, board images or reference values. Such material helps trace power rails, locate test points and diagnose shorts on stacked flagship boards. Match the model code, such as SM-G991B or a regional version, against the contents before using any 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 @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.