RAR archive of 183 KB labelled P5GC3L-BP, an ASUS desktop board model, with nothing in the name identifying the file type or PCB revision. Extract it and check the extension of the contents first. If it is a boardview, open it in a tool such as FlexBV or OpenBoardView to locate parts, inspect pin connections and find test points during fault finding. Compare the revision silkscreened on the motherboard with any version noted inside, since component placement can change between board revisions.
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 @boardview. 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.