Boardview for the iPhone 6S Plus logic board in BVR format, 323 KB. It opens in boardview programs that understand BVR and shows component outlines, reference designators and net connectivity across both sides of the board. Technicians use it to identify parts from a schematic, follow power lines from the PMIC, locate pads for diode-mode readings and find the culprit when a rail measures short to ground. Check the model and board markings on your device first, since variants may differ in small details.
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 .bvr file
Text boardview from the BoardView R family of tools, seen for Lenovo, MSI and Clevo boards.