Boardview package in a ZIP archive for board BM5070, apparently provided in both BDV and TVW formats according to the name. TVW files open in Teboview and similar tools, while BDV files work in many common boardview programs. A boardview lets you find component locations, pin nets and test points, which speeds up tracing shorted rails or missing voltages. Check that the BM5070 marking and the revision on your PCB match the file before trusting the part placement.
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 @cynetitsolution. Enginerys does not host this file.
How to open a .zip file
Compressed archive that every operating system opens without extra software.
Built-in OS tools7-Zip