Boardview for the MSI MS-7B78 desktop motherboard, revision 1.1, supplied as a 1.31 MB RAR archive holding a .CAD layout file. BDV in the name simply marks it as a boardview. CAD boardviews open in viewers such as OpenBoardView, FlexBV or BoardViewer, where you can search nets, highlight pins and locate test points. That makes short hunting and checking voltages around the VRM or chipset much faster. Revision 1.0 boards exist too, so verify the printed revision matches 1.1 before following part locations.
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 @BoardSchematic. 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.