ZIP archive, 233 KB, named TRKU with the token BVD, very likely a typo for BDV, meaning boardview. TRKU looks like a project or board code, but no brand or revision is stated, so check the contents after extracting. Boardview data opens in tools such as OpenBoardView or FlexBV for locating parts, following nets and finding test points. Compare the board code on the PCB with the file before relying on component positions.
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 @cyberlanelectonik. 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