RAR archive of 259 KB for the ASUS P5KPL-AM SE motherboard, a micro-ATX desktop board; the name does not specify the file type or revision. Small archives for ASUS board models like this frequently contain a boardview, which shows part placement, net names and test points and opens in viewers such as OpenBoardView. Extract and confirm the contents before use. The SE variant can differ from the plain P5KPL-AM in layout, so verify the exact model name printed on the PCB.
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.
7-ZipWinRARThe Unarchiver (macOS)