Boardview in BRD format for a board coded R23-MB-D. No laptop brand or model is given; the MB-D ending likely marks a board revision. The file can be opened in OpenBoardView, FlexBV or Boardviewer to show both PCB sides, part references and net connections. Technicians use it to find where a component sits, follow a shorted rail to its source and locate convenient test points. Match the board code printed on the PCB before relying on it.
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 @ITHINKHS. Enginerys does not host this file.
How to open a .brd file
The most common boardview extension. Several unrelated formats share it, which is why one viewer opens a .brd and another refuses it.