PDF schematic titled B150M-C RG, about 1.33 MB, with no brand recorded. B150M-C matches a micro-ATX desktop motherboard model using the Intel B150 chipset, and RG may be part of the board name or a revision tag; the name does not clarify it. Technicians use such a diagram to follow the VRM and standby rails, check the power-on path through the super I/O, and locate parts near a short. Confirm the exact model and revision on the PCB, since similarly named boards from different makers or revisions are not interchangeable.
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 @vinafix_bios. 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.