Boardview file in .cad format for a Quanta motherboard identified by the project code G3EC, revision D. The name gives no laptop brand or model, so confirm the Quanta code silk-screened on the PCB before using it. A boardview maps component placement, part designators, nets and test points, letting a technician trace power rails, follow signals between chips and locate the parts around a short. CAD boardviews of this kind open in viewers such as OpenBoardView, FlexBV or Boardviewer, and the 3.32 MB size suggests a full board layout.
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 @notebookschematic. Enginerys does not host this file.
How to open a .cad file
GenCAD text export, the usual format for Compal, Quanta, Wistron and Dell / HP / Lenovo laptop boards.