PDF containing PCB layout and schematic diagrams for the Nova 3i, presumably the Huawei Nova 3i smartphone, though the brand is not stated; the Bengali title phrase translates roughly as let us learn something. Phone schematics like this show power management, charging, display and RF circuits with component labels. Open it with any PDF reader to trace lines, identify test points and locate parts during board-level repair. Check the board version against the drawing before trusting component 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 @mischematic. Enginerys does not host this file.
How to open a .pdf file
The standard format for schematics, block diagrams, power-sequence charts and service manuals.