Schematic PDF with an uninformative single-letter name, B, so neither the device, the brand nor the board number can be determined from the name. It is an 885 KB document, possibly one part of a split schematic set, perhaps paired with a file named A. Open it and read the title block to identify the board and revision. Once identified, such diagrams serve for tracing power rails and signals and for checking component values, but always confirm the PCB number matches before using 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 @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.